Someone who gets salty in an argument of any topic and starts to lose and melts down in anger, frustration or just in general - losing.
Or
Picking apart the person with facts that she or he can give proof out. But your opponent can't counter, just saying stuff off of his or her dome and breaking down in anger or frustration.
That feminist Nazi is having a temper tantrum that men are stronger than her and breaking down. What a saltflake.
Someone who jumps from one relationship immediately into another one.
Serial monogamists can not stand to be alone and often suffer from vast commitment and insecurity issues.
Because they jump into relationships immediately after the previous one has ended, serial monogamists typically don't take the time to reflect on their behavior or why their previous relationships failed; thus, they end up making the same relationship mistakes over and over again.
Person 1: Damn, Dustin already has a new girlfriend?! It's only been two weeks since he broke up with his fiance! I think he's a sociopath.