Powers I got...
http://powerlisting.wikia.com/wiki/Meta_Regeneration
http://powerlisting.wikia.com/wiki/Cheshire_Cat_Physiology
http://powerlisting.wikia.com/wiki/Essence_Reading
http://powerlisting.wikia.com/wiki/Nuclear_Manipulation
http://powerlisting.wikia.com/wiki/Homo_Magi_Physiology
http://powerlisting.wikia.com/wiki/Telepathic_Force_Manipulation
http://powerlisting.wikia.com/wiki/Time_Manipulation
Okay... I think I just became the most powerful and unkillable member of the Avengers. Also my name is no longer Black Widow... it's Black Cheshire, or better yet Red Cheshire because of the hair and my new fur, because I am now a cat girl. If anyone has a problem with name change I'll just troll them with my powers for fun.
Scenario 1: Entering the world after the activation of the Avengers Initiative I probably cause confusion and concern to S.H.I.E.L.D. at Black Widow's sudden personality shift and physical transformation and basically turning into a god. First time I see Loki, he will not be hard to identify even with illusions/shapeshifting due to Essence Reading, I'm going to pull a Doctor Manhattan and explode him into chunky salsa. No doubt this will piss off Thor, but I don't really care because he can't kill me or harm me in any meaningful way.
After the business with the Chitauri is finished, if it even continues depending on the point I kill Loki, I confiscated the Tesseract and Loki's Scepter and remove the Infinity Stones inside. My Meta Regeneration abilities mean I should be able to safely handle the thing or at least come back from it exploding me. I leave S.H.I.E.L.D. because it's not like they can stop me. The Mind Stone should amplify my existing telepathic abilities greatly. The Space Stone will enhance my Cheshire Cat teleportation most likely.
Hopefully my powers give me some ability to understand and control the Stones properly. I then head to the New York Sanctum (Essence Reading will help me find it) and ask politely first, but if they refuse don't leave and annoy them until they train me in magic. I also spend this time to get a handle on my powers and the Stones. I of course hide the fact I have the Stones. Eventually the events of Thor: The Dark World are going to happen and I'll leave my training to go collect the Reality Stone. Again, this will probably piss off Thor and I'm probably going to have to fight him and pull my punches so I don't actually kill him.
When I have sufficiently trained and been admitted into their order and gained their trust and Doctor Strange shows up I go along with the story, but eventually steal the Eye of Agamatto and Time Stone within. I'm not sure how powerful my Time Manipulation powers will be to begin with, but I use the Time Stone to amplify them. I then use my Time Manipulation and the Time Stone to go back to the 80s to when Peter Quill was abducted and hop aboard Yondu's ship. I demonstrate my powers by killing a few Ravagers if they have a problem with me staying on board. Note that Meta Regeneration means that I can't have my existence erased from the time stream.
I proceed to follow Peter Quill around as he becomes Star Lord and act as a sort of Aunt figure and help train him and eventually become part of the Guardians of the Galaxy. When the whole business with the Power Stone happens, I take the Stone for myself. I try not to help Quill and the Guardians to much since I don't want to solve all their problems for them. I think Rocket wouldn't like me for intentionally standing on the sidelines and only intervening when necessary. Drax and Gamora might have a problem with this too. I think Star Lord would just kind of get used to it over the years.
Collecting Infinity Stones mean I am now extremely powerful and probably going to be drawing the attention of Thanos at some point, however he can not actually kill me and I can create Nuclear explosions unaided as well manipulate people's minds if they find out that I have the Stones. Also I can teleport to avoid Thanos. Really if I encounter Thanos... why I can't I just teleport him into a star? I'll survive that and can teleport somewhere, he can't. I can also probably mind rape him or something.
However I know the final Stone is on Vormir. I head there after collecting the Power Stone and wishing the Guardians well and head to Vormir. I have several options on trying to get the Soul Stone. I try each in this order if the one before it fails:
1. Blowing apart the shrine the Soul Stone is housed in. I would expect the shrine is less durable than the Soul Stone.
2. Traveling back in time to before the Soul Stone was enshrined on Vormir and claiming it then so I don't have to sacrifice anyone.
3. Waiting for Thanos to come to the Shrine and sacrifice Gamora for the Soul Stone, then taking it from him. I try to resurrect Gamora afterwards.
4. Try to sacrifice myself since I'm probably the most unkillable thing in the universe. I guess it's sort of like Odin sacrificing himself to himself. After all I do care about myself.
5. I probably care about Peter Quill like a son at that point so I would begrudgingly sacrifice him. However, the good I could do with the Stones would outweigh one life and also I could theoretically resurrect him with all the Infinity Stones.
Also at some point I may need to get a hold of the Infinity Gauntlet probably.
Do we have to go to 616 specifically? Can we go to another Marvel comic universe?