so alexei's main problem is that he sort of hates everyone and thinks they either can't or flat-out won't help themselves, and the corollary to the main problem is that once he's convinced that people are like that then it's probably better if they all die

he's also literally just got here off of a really, really bad murder-everybody bender in canon so there is also that

...basically he's highly, highly prone to teamkilling even without his personal demons running around, is what i'm saying here, and i'm very sorry

personally speaking he considers himself to have been betrayed a lot by various people, some more egregiously than others, so he will be seeing specific people that won't be helping with the desire to just blast the entire damn group to pieces to remove a certain threat

thankfully though on the other side of things he can usually keep the urge to teamkill in check

usually

and he's incredibly likely to stop once it becomes obvious that something is...amiss here

but yeah if you want to be on the wrong end of existing specifically just let me know o/