For me personally:
Lovatics vs. Selenators
Literally don't get this. Like, at all.
I think that both of them are great and can co-exist within the pop world but there's just not a single day where I don't see a shady thread created by a member of the opposite base on the other. Don't they like each other now/I thought they were cool with each other?
Also, (at some stage) the Hive vs. The Army. Like, what???