Godlike:
Worker 8 (FFT) vs. Magus (CT) - Very strong kneejerk without any further analysis
Heavy:
KOS-MOS (XS) vs. Lyndis (FE7) - EDIT: This fight comes down to form you are voting under (so recent discussions regarding specifying form matter here for sure)! XS3 form wins with either ultimate skill. Both Platinum Singer (90% damage cut) and Blood Dancer are bad for Lyn. On the other hand, XS1 KOS probably loses. S-Chain helps but it's locked to just one range. Which means Lyn can open with Bow + Bow counter. Even being generous and assume it hits (as NEB does), she then still has to make the next 2 attacks connect while hoping the other effects from S-Chain lands (they are not guaranteed other than the accuracy busting). Speaking of, S-chain only busts accuracy - not evade. So all together, KOS needs to connect like 3 times at subpar hit rates and can't miss once. While Lyn likely doubles too. So that's 4 hits off the bat before this RNG-fest. That's rough.
Maya Schrodinger (WA3) vs. Ernst (S5) - Bad news for Maya: Ernst can chip between physical hits and using the Beast Rune. Worst news: Ernst's L4 full heals him, so she needs to OHKO to win this and I kinda doubt that. Like, if this was Georg5's MDef, then yeah.
Ryuji Sakamoto (P5) vs. Tidus (FFX) - Yellow Shield blocks Zio skills and Skull's big damage is ST focused. This isn't getting to how he has no resistances to Tidus' speed game, so yeah, this is ugly.
Middle:
Mitsuru Kirijo (P3) vs. Karsh (CC) - EDIT: Mind Charge'd Bufudyne deals 546 damage to a 510 kill point (because P3 vanilla/FES Mind Charge is only 2x). Karsh has 113% HP and pretty much average MDef, so Mitsuru has no chance to OHKO with it. And while Chrono Cross physicals are never 100% accurate, Karsh would need to miss like an entire chain of L1s (which have like 90% accuracy) to give Mitsuru an opening. Karsh high 2HKOs, so all he's going to be doing is pressuring with a L1 physical chain. No.
Machias Regnitz (ToCS2) vs. Clive Winslett (WA3) - Petrifying Shell actually works here!
Leehalt Alceste (WA3) vs. Bowser (SMRPG) - To Bowser's credit, he does have cast best HP, but I'm not sure that helps much. EDIT: One turn of Bowser fear damage is not really enough, so yeah, Bowser has no way to make this work.
Albel Nox (SO3) vs. Shulk (XBC) -Don't see how Albel gets around Monado Speed or Shield. It's not like he has a Dispel and all his big damage comes off of named techs so Shulk will almost certainly have meter for it.
Light:
Marcus (FE6) vs. Mustadio Bunanza (FFT) - Agreed with user Snowfire - Guns are more akin to Siege weapons, so Marcus6 can't even counter them with Javelin. Without those, he has no hope.