I've never heard of this character, so I'm basing my decision on what summary Dalliah has provided.
This sounds pretty powerful, and from the description, it sounds like it can pretty easily pierce Iron Man's armor / body / whatever. That said, I don't know how accurate / fast it is...would it be able to hit Iron Man while he's in flight, and dodging?
Welp, this seems like a pretty overpowered ability, although the ending part does seem a bit less useful. But if this is useable in the fight, pre-fight, we might as well call the showdown here. If she can determine the fate of anyone, she can defeat anyone before they even start fighting.Fate Manipulation
Remilia has the power to control the fate of others and herself, though she does not like to use this power often. She practices it with little things and has gotten quite good at it lately. She finds it harder to use under extreme stress, despite that being when she'd normally need it.
Again, not enough information here. How does she manipulate it? How close does she have to be?Blood Manipulation
Starting out as a simple experiment, Remilia found she could manipulate blood. Though she rarely uses this ability, she finds it useful to keep in practice in case she ever actually needs it.
Not quite sure what this means, either. Does it strengthen her? Harm enemies?Darkness Manipulation
After being possessed by a sort of darkness, she began using her fate manipulation to learn to control it. It's difficult, and she sometimes believe it will possess her again, though she's managed to hold it off so far. It takes a lot out of her to use this, so she usually only uses it when she is desperate.
Sounds like when in Dragon Ball Z, when Saiyans see the moon, with their 'tail intact.Power Boost
Remilia gets a serious boost in energy when the scarlet moon is in the sky, and an even more powerful boost when she looks at it. This causes her to lose her sanity, though, and go on a rampage. Sometimes she might even try to manipulate fate and keep the scarlet moon at the sky when she is in this state, though she usually regains her sanity in the middle of a rampage either by fighting her insanity or not looking at the moon for a long period of time. Lately she's been trying to fight off the effects of the scarlet moon when it is up, despite visibly struggling to do so.
Overall, while I don't know much about "Remilia Scarlet", it sounds like she's pretty overpowered. She can manipulate people's fate, which just flat-out isn't fair. But all-in-all, sounds like she could defeat Iron Man. Voted for her.
Also, agreed with Vellus. I have no idea who this person is, and I haven't been "living under a rock".