Been quite a few in the 4 years or so I've been playing. Let's see...
Unchained
RoLe made a return about 3 years ago and made an alliance called "Unchained". It had Tok, Role, Ippo4ever, Grap, briefly, some other guys. Lasted maybe 6 months and a few alliance events. Eventually it split and several of the guys merged with SFL.
TRT
Jid created an alliance called TRT about 2 years ago. Had a lot of newer players in it but he couldn't seem to pull in enough vets. Lasted a few months.
For We Are Many
Judo made an alliance about 2 years ago where everyone changed their forum name to start with Brother, like Brother Judo, Brother Chuckiceman, etc. Last a few months, kind of had the same problem Jid's had, didnt get enough vets swung over.
TNG - The Nice Guys formed at the beginning of 2017. SFL had done very well through the bulk of 2016 with a team ending up with Tok, MMAPhreak, The Captain, Ungrateful Dead, Chris Hansen, Wankrupt, Hector, Cumoneileen8, Rugbythug, Simonh10, Outlaw2187, JeyJey, BeatnikHusker, and myself. It was time to mix things up.
Biz had recently left CC and was looking to form an alliance. The Captain and Ungrateful Dead Joined him to form the backbone of one of the top alliances through all of 2017.
Alliance deaths -
The Company
Long one of the top alliances in the game The Company closed up shop around March 2017 during a bout of inactivity. Since then many of the core ex-company members have returned and joined groups such as SFL and TNG.
Chaos Crew - Long standing competitor Chaos Crew merged with THC around August 2017 to form one larger group. This combined team remains competitive today.