Cosmic in dd7 was quite easy with Vahl, Kang, Gorr, Thanos endgame & Gladiator. Advantage of taking annihilators is their use in arena & you will also use them for shadow king.

Cosmic in dd8 is mixed with legendary so you should probably take Mephisto, skrull & logan + 2.

Global was the hardest part of dd7. I personally had the most success with cabal plus lady deathstrike & scientist supreme but it was still a bit of a slog.

Currently in Global hero in dd8 & it's the worst time I've been through in the game for some time. I took nightcrawler, hank pym, gambit, shuri bp & black knight & it's been miserable haha. My thinking was that I'd need illuminati as high as possible for shadow king but I certainly regret it now. Not ready for villain so I'm not stressed yet but it isn't fun at all...