If more than one person has thought you are a jerk, especially more than one at a single job, and you don't know why, you're probably a jerk. The classic sign of a jerk is someone who can't pinpoint why someone would think they are a jerk in the first place. Or worse, you know why but you just don't care.

As far as toxic workers go (jerks included), there are a lot of reasons they are toxic:

* They are negative all the time. They sap the enjoyment out of the room. * They are highly critical of other's work. No one else has a problem with the work others are doing, they just nit-pick every little thing. * They avoid hard work and only go after prestige projects. They'll try to push stuff like maintenance work onto others, and half-ass it when they have to do it. * Anything they do wrong is met with a strong defense mechanism and a need to deflect into someone else.

I'm sure there's more, these are just off the top of my head. Contrary to belief, being 'brilliant' has absolutely nothing to do with whether someone can be toxic. I've met a few toxic people in software and out, and some were downright mediocre.