As far as Entities go.
offhand.. and I'm sure Mr. Master will correct me
I have two lists
1. The One Above All (TOAA) (In theory he is the supreme being of the marvel, ie "marvel" megaverse. see my second list for my thoughts on TOAA)
2/3/4/5 (tied). Multiversal Eternity/Multiversal Infinity (represents time and space of marvel multiverse)/Multiversal Death(tricked/defied living tribunal)/Living Tribunal (Supreme Judge of the Multiverse responds to only one being)
6/7/8/9. Abraxas and the Infinites. Abraxas's mere existence affects the multiverse and is birthed from within Eternity. He is only killed by erasing all of multi-eternity, but could not kill multi-eternity without the aid of the ultimate nullfier, signifying he was strong enough to affect multieternity, but not strong enough to kill him on his own. Also without the multiverse, he ceases to exist. The Infinites (there were supposedly 3 of them) work to align the energies of the multiverse. They manhandled single Eternity like he was nothing. And they were apparently a facet of multieternity. This could be similar to the way the celestials are part of single eternity and Galactus is a part of single eternity. (abraxas being the galactus of multiversal eternity, and the Infinites being the "celestials" of multiversal eternity)
11. Roma Omniversal Guardian (descendant of Merlyn, who eventually took his place)
12. Saturyne (previously second to Merlyn, then Roma when Roma took over)
10. Atleza (Juggles our universe without care)
Including Items and preretcon....
1. TOAA (In theory he is the supreme being of everything so noone is possible to being greater than he is, greatest being of the Megaverse. All universes and multiverses related to, even if distantly related to, the marvel universe. IE TOAA is master of even the Utraverse, which is also a subsidiary of marvel, Therefore TOAA must be supreme being of the "marvel" megaverse.)
2. Pre-Retcon Beyonder (powers of millions of multiverses, but never states megaverse. In fact he may come from outside our multiverse, but from within our megaverse.
3. Pre-Retcon Molecule Man (only being capable to standing up to beyonder,
4. Thanos with HOTU for having EASILY absorbed all that was withing his realm, including the living tribunal
5/6/7/8/9/10 Multi (Death/eternity/infinity)/Living Tribunal for reasons stated above. Infinity being (was originally the only being around, from its death, and the core of its being came reality (the multiverse) as we currently know it. Lastly we have the infinity gauntlet, which was the power of the infinity being, and any being that had it could defy living tribunal. however without a will behind the gauntlet, tribunal was able to will the gems powers never used again. Had the owner (adam warlock) resisted, living tribunal may never have been able to depower the gems.
btw. After making my statements on the comic omniverse which includes dc. the marvel megaverse which includes the marvelverse, ultraverse and new universe/new universal (includes characters such as starbrand and nightmask). the marvel multiverse (which includes marvel continuity and out of continuity comics such as what if? Marvel the end. and other spinoffs. The marvel universe includes all comics in current marvel continuity.
I just realized that, just now, that there apparently is an article on wikipedia if you look up marvel and multiverse.. that states almost verbatim, everything i've been stating for months. I'm not saying its true. But man if i don't suddenly feel justified for my thoughts.