OK, so Terry.
To start with, don't compare him to Ryu and Ken. Ryu and Ken have the Luigi design where they have a hard time getting in, but once they get in, they do massive damage. Terry is even slower than those two for raw stats (less than 1.0 air speed, slow dash), but he has 4 burst-mobility specials (Power Dunk, Burning Tackle, Crack Shot, and are-u-ok in Go!), and an incredibly beautiful dash attack for burst. When he uses one of these, he goes from being bottom 5 mobility in the cast to top 5, so his archetype is automatically way different from Ryu/Ken: Terry is a whiff punisher.
His back dash is actually crazy good for this purpose; the little hurtbox shift that he does and the short distance he travels and just how quick it is combines with his burst options to let him whiff punish any attack in the game. For example, Lucina landing n-airs (which is usually very safe) and Terry back-dashes into Crack Shot, and at most spacings it doesn't matter if she gets out the shield in time or not, he'll just blaze past her even if he doesn't hit her.
It's kind of hard to approach Terry. Power Wave is a good projectile; low-profilers like Inkling and Pikachu have to come at you the traditional way, so you can use it to force a jump, and because of Terry's burst mobility, jumping isn't that safe. Crack Shot just eats up most jump ins that don't already have a hitbox going when he uses it.
Approaching slowly with shields is the way to go, but then, as it turns out, you're playing Terry's game. Up close, Terry's frame data is a bit slow and he's not safe on shield, but it doesn't matter. The thing is, you can't react to anything that he's doing up close, and if you guess wrong or if you mis-space even slightly, you take more damage than he risks taking. He can spotdodge cancel into a kill confirm, he can jab you for 40%, or he can just use one of his invincible options for a quick 20%.
If you're someone like Fox and you're going aggro on Terry and n-airing and jabbing, you're playing the wrong side of the risk-reward table, even though you're so much faster up close. Terry just has to mash buttons to be completely random with what he's doing and you will get hit, and you will take a ton of damage. Your best bet is punishing OOS, but in that case, if Terry has Go!, you're just Gone! up-tilt Power Geyser ravages shield.
Terry's crouch is actually a hidden top-tier tool too. d-tilt may not be safe on shield but it confirms into so many options, and if you attack him, Terry has two sources of invincibility directly out of crouch--he can spotdodge and dodge attack, or he can Rising Tackle. Spotdodge covers your grounded moves and Rising Tackle anti-airs. For similar reasoning, Terry's OOS is amazing--you can spotdodge directly out of shield and follow up however you want; summoning more than a dozen frames of invulnerability out of an already strong defensive position and possibly getting 40% or the stock for it? That's insane.
Terry in neutral is overall great, and he gets enough reward off of neutral conversions and being up close that even if his advantage state (juggling, ledgetrapping, edgeguarding) weren't that great he wouldn't need it to be. But his ledgetrapping in particular is actually pretty good, since you can't really roll behind him unless he's in the middle of an animation. He can just stand near ledge shielding and as soon as you do anything other than jump, he can spotdodge and cancel it into a power move. With Go!, he edges out just about every other ledgetrapper in terms of lethal mixups.
So, for archetype, Terry is one of the slowest characters in the game who can, while whiff punishing, be one of the fastest, and gets huge reward off of being close to his opponent. You can't whiff against him, it's hard to zone him, you can't approach him, and you don't get as much reward as he does once you've actually approached him. That archetype actually hasn't existed in smash before, but from my experience playing it, I can tell you that it's probably viable against every other archetype in the game.
But Terry has two obvious problems. One is that some zoning characters like Megaman actually don't care about Power Wave or even Crack Shot and can force Terry to commit really hard to a burst option to get in, while never needing to go in themselves. Those matchups are likely difficult.
The other (and you've probably already heard this from different people) is that he doesn't snap to the ledge with most of his specials. Terry does have some options to mix up his recovery (invincible Rising Tackle, Crack Shot, Power Wave stall, etc.), but his air-speed is bad. Compare to Chrom who can often airdodge to ledge by virtue of his insane air speed and avoid the edgeguard attempt altogether, but still loses his stock sometimes while recovering, and it's a bad look for offstage Terry.
On the bright side, Terry does deal pretty decently with other forms of disadvantage such as being ledge-trapped and certain juggling situations. His burst options, invincible options and spotdodge canceling are great in those bad situations, and 108 weight can allow him to come back through Go! if they end up going poorly for him.
I'm going to predict that he's actually pretty good, somewhere in the high tiers, maybe a bit shy of top tier. For Terry to be top tier, his recovery game (not his punish game, which is what everyone is working on) needs to be optimized on a per-matchup basis. No one ever labs disadvantage. But that's what the Terrys are going to have to do if they want to have that top 10-15 status. And it's possible (though somewhat unlikely) that he's just OK enough to get there.
GOODBYE.
and 
