"Throwing shit can be hit away."
And sword strikes can be blocked. Or outranged. Even easier than sword strikes. Two can play that argument. Also unhealthy? What the eff do you think this is, a drug addiction? This is a debating website.
"Everything Ikki has is shown."
No it's not. He's a LIGHT NOVEL character. Nothing he has is shown, unless we count the anime adaptation. It's all text, genius. and even then, the only reason Ikki tops this list is because of normally unquantifiable things that goes "But this takes a lot of skill you guys!" Next you're gonna see something like "I regrew my body from nothing by sheer skill now I'm secure at the top" or something like that. Ikki ain't unskilled by any means, but show actually quantifiable things that don't have the LN staple of language that's more flowery than a freaking garden.
You know, with how much you suck off Ikki and his fate, Im surprised you're not gravitating towards the fact that one, the dude was explicitly shown to have gained skill from it, and two, this is Marvel, where herald level shit at minimum is recorded in it every day. You have intimate knowledge on things like Galactus and Beyonder but not on kung fu. Makes perfect sense to me.
"Seeing possibilities"
Sure, at some level it's skill. Reading your opponents is skill. To a certain extent. I bait you into moving right after grooming you with my left. I've played enough Smash to know that it's skill. And then it just becomes straight precog. Which is what all these feats eventually become. But you know, they say skill so you instantly gravitate towards it. Heck, even if I concede that it is entirely skill, Ikki would still lose to Musashi due to her possibility stuff. And Bill Cipher. And Black Zetsu, who predicted millennia into the future.
"Poseidon"
And I'm not saying it's not cool. But it's still the epitome of plot. If someone can blitz you a thousand times over, you're not winning. Period. Like what, is Spider-Man besting the MFTL+ Thor something to top the list? Wonder Woman could catch an immeasurable in her lasso. Does she top the list?
"Caught thousands of afterimages"
Aight so every danmaku character should be number two. Can't wait to see it overpopulated with Touhou, Undertale, Gungeon, etc., or Sora and Riku blocking hundreds of beams of light. Is it cuz Poseidon's faster? If so, see above.
"Water bottle and billiards"
Amazing strawman, dude. Tell me, which one has actually been used for combat before?