I wasn't around for GGA at their worst, so I'll throw in some of my own alliances I've dealt with:
- TPF: Bailing out of a blood pact with the Unjust Path and then going on a witchhunt that destroyed the OOC/IC line. Routinely under horrid leadership.
- M*A*S*H: Got matched up with Umbrella in the Bipolar War and ended up getting a damage dealt: damage received ratio of 1:10 (yes I'm serious). Disbanded shortly after.
- Poison clan: Being allied to them was a PR nightmare. It wasn't so much that their leadership was bad, but there were several incidents that always gets people asking "why are you allied with them?" Such as sheltering the RIA hacker fiasco, the NEW raid crap, and the stuff regarding the NAP with TPF (which was smart of them to do, but most of the world hated it).
- MI6: some would say they're too new to be on here, but the personalities they attracted made them one of the worst PR alliances and it's already biting them in the ass.
- The Legion: Won worst alliance in 2010 and for good reason.