It's almost 5 AM and I'm tired, so I'll add more thoughts to this later, as well as other stuff.
Now, going back a few pages, I see Pierce pretty much left the thread, so there's no use asking him why exactly Mario is considered C-Tier for him, but as for me, he's a D-Tier character, for now.
I've already done a very heavy analysis on Mario way back when, and even now nothing has changed. While his metagame is not at a halt, it's pretty easy to realize that Mario isn't a broken character (minus shenanigans you can do with the cape and fludd) with a plethora of options like Diddy and Snake. He does have answers for just about every character except DDD, but thing is these "answers" are often not very strong ones due to his natural limits that cannot be bypassed, just covered. Just about half the characters in C, and the large majority in B, A, and S can handle the same situations in a similar manner to Mario, just better. This can't be overlooked when handling Mario's placement. He's quite literally the middle-man character, heavily emphasized by the fact he has the most even match-ups in the metagame. And I think that's enough to say on that.
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As for people saying Diddy could be the best character in the game: Why? Are you treating him like Melee Fox, where at his fullest potential he's an unstoppable beast, but no one will -ever- get to that potential? Lets be serious here, Diddy has obvious weaknesses. His banana game is awesome, but it's coin sided by obvious facts.
-His Bananas can be caught, picked up, and used against him.
-His air game is average, alot of characters outrange and outspeed him, and bananas can only flinch in the air.
-A gimpable recovery that usually can be done by a disjointed attack, and then there's the large cooldown between Up-Bs.
Diddy being the potentially best character in the game is outrageous, same with Falco, although he's more believable. I also don't believe Diddy is S-tier material. He should be A-tier, probably at the top.
I don't see IC being S-tier either. There's many attacks that zone them and separate them, and once separated it becomes an uphill battle to resync or to SoPo. There's not much else to say on this, because that's their biggest hinderance and should really be the only reason why they're not S-tier.
Lucario should be B-Tier. He's definitely not a C-tier character, especially with his Aura shenanigans and damage control. He's also a pretty good gimper, and can rack up damage pretty quick when he's behind. That makes match-ups with him very tense because they can never take a break. Lucario can easily come back and he can also keep the lead if he does have one.
Ike's placement is correct, but the synopsis is misguided. It's been said a 1000 times over in this thread, so I won't bother saying it again.
Link can potentially rise to E-tier. He has alot of force to reckon with, but generally it's agreeable that his recovery is just too exploitable for any character besides a given few. I do believe his KO ability is overlooked. U-tilt, F-tilt, D-Smash, F-Smash, Up-B, and N-air are all decent kill moves with U-tilt for me being the most useful kill move. Link's main problem outside of his recovery is his damage racking and generally having no answer to being comboed besides SDI.
4. Marth has a "solid recovery"... ???
Marth's recovery while telegraphed is hard to punish due to his disjointed range and aerial speed. DI for the most part will always allow him to make it back on the stage. His Up-B is also really hard to contest due to it's incredibly speed and ledge snap. Despite this though, Marth can be gimped and is vulnerable offstage, especially when projectiles are put into play. It's solid, but not great.