It’s difficult to work with someone who always seems to be aggrieved. It’s a sign they will blame others rather than take responsibility themselves. It’s also a sign that they won’t be interested in improving their performance or making adjustments to collaborate better with you or the team.
If someone is perpetually aggrieved, it’s just a matter of time before they start blaming you for treating them unfairly. If that someone is particularly persuasive (it’s easy to get sucked into), it can have a far reaching, negative pull on everyone.