Hmm... I have no idea how to fight a good Bowser Jr. How do I approach, specifically, getting through his walling with Fair? What can I punish? What do I do when he's above me planning to use one of his Dair combos, if he aims to land behind me so I can't shield grab him?
Also, the Ryu matchup seems more annoying than I thought, entirely because of his Focus Attack dash cancel and True Shoryuken. Focus Attack allows him to stay mobile while having armored frames, and True Shoryuken can be used out of a dash to bop us when we go for an aerial approach. Since Ike has very few multi-hit attacks, it becomes an infuriating guessing game of trying to time when it's safe to go for an attack. So how do I deal with a Ryu using lots of Focus Attack?
As a former Bowser Jr. main, I can sum up some points.
1) Don't try to challenge his Dair with Nair. That damn drill will get you from above.
2) Jump-Z grab the Mechakoopas. They hate when you use their own weapon back at them.
3) In spite of the Dair, Bowser Jr. is combo food. They get juggled greatly since they're as heavy as us.
4) Uair will combo from UThrow for a true kill at 101%, just like with Captain Falcon. Maybe even a little earlier.
For Ryu, I can't give you anything solid, only prospective. I've only faced one on Smashladder, but he wasn't very good. I would figure it's more productive to stay in the air and use plenty of grabs to avoid FADC. Getting him off stage is necessary.
PyroTakun
Having played a Diddy at HotS today, I can bet you likely choked against Diddy. They will put so much pressure on you it's not even funny. I know this because Stockfield took my first game and 2-stocked me. But I managed to pull back.
1) If he has the Banana, let him have the banana. There is nothing you can do. Once he loses it, that's your cue to strike. If he throws the banana at your shield, you can jab him since he's coming in for dash grab. DTilt works if he's at range.
2) Diddy is bait for UThrow into Fair/Nair. He combos like no other. Use as many grabs as you can since they rely on using safe moves to bait you and shieldgrab you.
3) Be patient with the Peanut Popgun camping. Not much you can do. You could tomahawk grab over a peanut since you know he's going to shield. Dash-shielding also works if you perfect shield.
4) Be wary of your Nair usage. His Fair is the best in the game for being long-ranged and comes out super fast. However, it's your best spacing weapon as always.
5) Your best punishment opportunities come from his whiffed or shielded Smashes. I'm sure you know what to do here.
I find it very hard to gimp Diddy for a number of reasons. He's overall very unpredictable. However, they're so easy to juggle and combo it actually puts us in a favorable position the moment we hit a Nair.