Ganondorf: Honestly I think the matchup is extremely similar to the Falcon matchup except Ganon just doesn't do it as well as Falcon. His strong blows can separate the ICs but he lacks the ability to capitalize as well on that as Falcon can. He can't pressure/overwhelm them like Falcon can and his lack of speed makes him easier to grab.
(based on experience vs. Phish-it)
DK: DK gets *****. The only thing he really has going for him is bair camping but that really isn't all that hard to get around when you have blizzard/ice shot and a really good shield game. Pretty much all of ICs' combos work on DK since he falls pretty quickly and he's a huge target, but he can't really combo them back. Getting a grab on DK is ridiculously easy since it's so easy to punish / approach him with a jab as long as you aren't being an idiot and running into a bair.
(based on experience vs. Phish-it and Kwan)
Fox: imo this is pretty awful and the only reason it isn't worse than 30:70 is Fox can get messed up really badly with a single mistake. He's like Falcon only Shine wrecks them even worse than all of the stuff Falcon can separate them with (Shine also makes him unusually hard to grab). A shine anywhere near the edge will send one of them off the stage and even if the IC avoids the gimp, you can only recover so safely with a single squall and Fox can capitalize so easily from it. Fox also totally outprioritizes everything except smashes and up-tilt, and once he gets in you get shined then it takes at least half your stock to gather yourself and regain momentum. He can also effectively counterpick them to pretty much anywhere.
(based on experience vs. PC, Sensei, Eggm, Kip, Swift, many more)
Marth: ICs are actually surprisingly good at getting inside due to their shield game, and it's pretty evident in a lot of Chu matches. Uair is great at exploiting Marth's weaknesses from below. Other than that Marth is still pretty tough just cause of how good a character he is and he's really good at camping them, poking away.
(based on experience vs. HBK, Emblem Lord, Sol, PC, and a bunch of other Marths)
Peach: I probably won't be saying anything new here. Peach's down-smash wrecks them (spins Nana backwards so she can't grab the ledge), she's almost impossible to approach and punish when using FC'd aerials, she outprioritizes just about everything, she can camp them really well, etc. On the plus side for ICs, shielded down-smashes can be punished with a grab (death) and with the exception of Mute City, they prefer similar stages.
(based on experience vs Ryoko, Bailey, Cort)
Luigi: He's one of the few characters who can beat them on the ground. The fact that both characters have bad traction really makes it tricky for ICs to punish anything since either or both characters will slide away when, for example, something gets shielded. Luigi's extra speed with his wavedash and down-b allow him to punish things the ICs can't. He's also really hard to combo yet he can combo them well. They share counterpicks.
Samus: The matchup is a lot more even than people think it is. Ice Shot spam can compete with Missile barrage as long as you make sure you shield a little early so Nana doesn't get hit to the delay in her actions. Samus is really slow in both the air and on the ground, so she can't exploit the ICs' air weakness but can get overwhelmed on the ground as well once they get past the spam and tilts. In the air she has a hard time dealing with Uair. ICs' strength negates Samus's survivability. They share counterpicks. I still say it's in Samus's favor because once she breaks the ICs momentum she can do some serious damage before they regain control and Nana does get gimped by missiles pretty easily.
(based on experience vs. Bino, Alukard)