Thanos and Darkseid is a hole different thread. Concerning the other villains, Marvel has Doom, Magneto, Ultron, Klaw, and Dr Octopus working and putting their brains together...thats a pretty a pretty deep bench...last time Doom got with Klaw he beat Galactus and the Beyonder...Klaw is one of the most under rated villains around...his raw power is pretty intense.
seriously... and if Doom can advise the Absorbing Man on how to use his powers he'd be pretty freakin' hard to beat... team him up with Ultron and he's got a constant source of adamantium to draw from
dr.doom and thanos in the same team thats overkill imo.if you wanna see who is gonna win just look at the leaders thanos and jobbersied please jobbersied cant even mess with dr.doom or magneto.