I think it's between Brainiac and AM. Brainiac seemed only nearly universal in the Doomed arc (while AM was confirmed to have been absorbing entire universes' energies) yet futures end is implying that it was merely a small aspect of Brainiac's true self, and with him being responsible for the Convergence event....i dunno, maybe he'll outperform even AM.
Darkseid is implied to be abstract-level (especially with the Batman/Robin arc canonizing FC) yet struggled against the JL and is about to get beaten by Batman with his new armor. So i think he's the weakest here.
He may be facing AM with the power of ALE, Soulfire, or any other potential amp he could get his hands on. Personally, i don't see regular DS matching AM. Especially with the energies of entire universes at his disposal. But i could be wrong i guess we'll have to wait and see.
Let's also not forget that DS is facing against Hellbat suit Batman; and it's not looking good for him (judging by the fact that Bruce succeeds in resurrecting Damian).
He's also got a showdown in E2. And he's not exactly facing against any cosmic level characters.
Along with the very first JL arc where a rookie JL drove him off...
So i have my doubts regarding DS being on AM's level.