By "toxic" I mean someone who essentially sees social situations as a way to play out their inner sadistic tendencies - for example by passive-aggressively seeking conflicts so they can play the victim, or constantly looking for "enemies" and trying to ruin their reputations. A person who has unresolved inner conflict or trauma which they try to rectify (or distract themselves from) by projecting issues onto others.

This is rather lite-pop psych, but covers the basics:

https://www.psychologytoday.com/blog/in-flux/201608/8-things...

Manipulative, judgemental, fail to be accountable / responsible, don't apologise, are inconsistent, require you to prove yourself, require you to defend yourself, are not caring / supportive / interested in what's important to you.

Not mentioned: there's often trauma, abuse, fear, or pain underlying the behaviour. Not that this makes it any easier to deal with.