I once managed someone who was genuinely exceptional at their work and clients absolutely loved them. They’d specifically request them for projects and even when the point of contact moved companies, they asked for this person to be their lead again. Their output was consistently top notch.
But…
I would be cc’d on emails (or forwarded them) that subtly undermined colleagues’ work. In team meetings, they’d dismiss ideas with a quick “that won’t work” before the person had even finished speaking. Then, three weeks later, they’d present essentially the same idea as their own. When junior team members asked for help, they’d get a heavy sigh and a response that made them feel stupid for asking.
I noticed the pattern slowly. First, people stopped volunteering to work on projects with this person. Then I’d see team members physically tense up when this person entered the room. Then someone really good resigned and directly cited this person in their exit interview. They weren’t the reason that they left, but they wanted to let me know that this person didn’t make for a great working environment in their opinion.
I knew what they meant. I’d known for months.
But I kept telling myself: “But the work is brilliant. But the clients love them. But we can’t afford to lose that revenue.”
I let it go on far too long because I couldn’t separate the quality of someone’s work from the quality of their impact on the wider team.
If you’ve got someone like this on your team right now, someone whose individual brilliance is causing team-level damage, this is one of the hardest management situations you’ll face. Because the results are real. The revenue is real. The client’s praise is real.
But so is the slow erosion of everyone else’s morale, collaboration and willingness to stick with you. They may also question you as a leader for tolerating this person, especially if they don’t directly see the brilliance that you see – they only see the attitude.
Today, I want to talk about why we let high performers get away with toxic behaviour, what the actual cost is (not the cost you can see, but the cost you’re missing), when it genuinely becomes a problem you need to solve and the specific conversation you need to have.
Why high performers get away with toxic behaviour (and why we let them)
Let’s start with why this happens in the first place. Because you’re not a bad manager for struggling with this. The reasons we tolerate poor behaviour from high performers are completely understandable, even if they’re wrong.
The results shield
When someone is genuinely excellent at their job, we excuse behaviour we’d never tolerate from average performers. It’s that simple.
If a middle-of-the-road team member was dismissive in meetings or undermined colleagues, you’d address it immediately. But when your top biller does it? “They’re difficult, but they’re brilliant” becomes the internal justification.
The results create a shield. Every time you think about having the difficult conversation, your brain immediately counters with: “But look at what they delivered last week. But look at that client feedback. But look at those numbers.”
The cognitive dissonance is real. How can someone who produces such good work be bad for the team?
The client love problem
This is the one that really traps you. If you work in-house, then it may be a stakeholder that loves them.
When clients specifically ask for this person by name, when they praise their work in review meetings, when they tell your boss how brilliant this person is, it feels impossible to address the internal damage they’re causing.
You’ve got external validation coming in constantly. The people paying your invoices think this person is fantastic. How do you square that with your team telling you (directly or indirectly) that working with this person is miserable?
The external signal is louder and more visible than the internal one. Client praise happens in meetings your boss attends. Team frustration happens in quiet conversations and eventually, exit interviews.
The hidden cost of ‘brilliant jerks’ (that you’re not seeing)
Right, let’s talk about what this actually costs you. Not the obvious stuff, the hidden stuff that’s quietly destroying your team whilst you’re focused on the brilliant work being produced.
The slow erosion of your best people
Your high performers aren’t leaving because of one dramatic incident with the difficult team member. They’re leaving because working alongside someone toxic is exhausting and they have options.
They don’t put “leaving because of a difficult colleague” in their resignation letter of course because it’s almost certainly not the main reason for leaving. But the chances are that the environment that they’ve been working in isn’t what they want in the long term – and the problematic star performer is contributing heavily to that.
The permission structure you’re creating
When you tolerate poor behaviour from someone because of their results, you’re teaching your entire team what actually matters. Not your values statement. Not your talk about collaboration and respect. Your actions.
What you tolerate, you endorse. It’s the same for any kind of performance or standards.
If the brilliant jerk dismisses people in meetings and nothing happens, you’ve just told everyone that results matter more than behaviour. If they take credit for others’ work and you don’t address it, you’ve just taught your team that getting ahead matters more than integrity.
Your team is watching this constantly. They’re learning what the actual rules are, not the stated ones.
As we’ve said before, as a leader, you’re always on stage.
The collaboration tax
Here’s the maths that finally made me see this clearly. (I’m emotionally led as a leader but also a maths geek, so sometimes I need more of the latter to help me work stuff out).
Let’s say that person is a 10/10 individual performer. Genuinely exceptional at their core work.
But if their behaviour makes three other people 30% less effective (through stress, reduced collaboration, defensive behaviour, time spent managing around them), you’re net negative.
One person at 10/10 doesn’t offset three people dropping from 8/10 to 5/10.
This is the same principle that I once saw Dharmesh Shah speak about regarding people vectors.
One brilliant individual who isn’t aligned with everyone else can prevent everyone from moving forward.
When it actually is a problem you need to solve
So how do you know when this crosses from “difficult personality” into “genuine problem you need to address”? Because not every interpersonal friction requires intervention.
The exit interview test
If you’re seeing patterns in why people leave, that’s data, not coincidence.
One person mentioning “wanted a more collaborative environment” or “different cultural fit” in an exit interview is an anecdote. It might be about them, not the team.
Three people saying it? That’s a trend you’re choosing to ignore.
I once made the mistake of overlooking some exit interview feedback and came to regret it six months later when other colleagues were now saying the same thing.
The meeting room silence
Pay attention to what happens when this person speaks in team meetings.
If everyone else goes quiet, stops contributing ideas, or suddenly becomes very interested in their laptops, that’s not respect. That’s people protecting themselves.
You’ve lost psychological safety, which means you’ve lost the conditions for good collaboration.
The “ask for feedback” gut check
Here’s a simple test: Would you genuinely feel comfortable putting this person forward for 360-degree feedback from their colleagues right now?
Not “would you do it because it’s policy” but “would you feel comfortable with what might come back”?
If you’d hesitate because you’re worried about what their colleagues would say, you already know there’s a problem. Your instinct is telling you something. Listen to it.
The conversation you need to have (not the one you’ve been avoiding)
Right, let’s get into the actual conversation. Because you can’t fix this by hoping they’ll somehow realise the impact they’re having. You need to be direct.
Although there was one time when a senior colleague got a little drunk with a problematic colleague and told them to stop being a… you can fill in the blank. This probably isn’t HR approved or something I’d encourage, but it did work…
Name the specific behaviours, not the personality
Do not say “you’re abrasive” or “you’re not a team player” or “people find you difficult.”
Those are character judgments and they’ll immediately make someone defensive. They’ll also give them nothing concrete to actually change.
Instead, name the specific behaviours you’ve observed:
“In Monday’s meeting, when Sarah presented her idea about the client campaign, you said ‘that won’t work’ without asking any questions or offering to build on it. This is the third time in two weeks I’ve seen this. In the project review last Thursday, you presented the social media strategy as your own work when I know it was collaborative with two other team members.”
Specific. Observable. Factual.
The SBIA framework is very handy here for these types of specific situations.
They can’t argue with what happened. They might argue with your interpretation, but they can’t deny the behaviour itself.
Connect behaviour to impact, including the impact on results
This is critical. Don’t just say “this behaviour is bad.” Explain the actual impact it’s having.
“I know you deliver exceptional work individually and clients value your strategic thinking. What I need you to understand is that your approach in collaborative settings is making other team members less likely to share early-stage ideas, which means we’re missing opportunities to refine and improve work. It’s also why the last two new starters asked to be moved to different projects after one month on your accounts.”
Connect it to things that are very real and impactful:
- Team effectiveness.
- Collaboration quality.
- Retention (if relevant).
- The business outcomes you actually care about.
The person needs to understand that this isn’t about being nice for the sake of it. It’s about their behaviour actively undermining the results you’re all trying to achieve.
Make the expectations clear and measurable
As with any feedback, the change that you’re asking for needs to be very clear – especially when it comes to behaviours.
“Be nicer” is not an actionable request. “Be more collaborative” is too vague.
Get specific about what needs to change:
“In team meetings, before you critique an idea, I need you to ask at least two clarifying questions about it. When you disagree with an approach a colleague is taking, I need you to present that feedback to me privately first rather than in front of clients or in team meetings. When you’re working on collaborative projects, I need you to clearly acknowledge others’ contributions in presentations and emails.”
These are observable, measurable behaviours. You can check whether they’re happening or not.
Set up the follow-up process
“We’re going to check in on this weekly for the next month during our one-on-one meetings. I’ll be observing team meetings and I’ll be asking for feedback from people you’re working with closely. I’m happy to support you in making these changes, but I need to see progress.”
Make it clear this isn’t a one-time conversation. You’re going to be paying attention and following up.
This week, I want you to do two things.
First, ask yourself honestly: Do you have someone on your team whose individual brilliance is causing team-level damage? Not just someone who’s occasionally difficult (we’re all difficult sometimes), but someone whose behaviour is creating measurable problems you’ve been excusing because of their results.
Be honest with yourself about this. If you’re even wondering about it, that’s probably your answer.
Second, if the answer is yes, book time on your calendar this week to write down specific behaviour examples. Not impressions. Not personality traits. Actual instances: what they said, what they did, what the impact was.
You can’t have the conversation without the specifics. And you can’t keep avoiding the conversation while your team quietly deteriorates around this one person’s brilliance.
The conversation won’t be comfortable. I know that. But neither is watching your best people leave because you prioritised one person’s output over everyone else’s experience.
