Piplup (Diamond/Pearl) vs Sandy (FF4): Sandy's not puny against the confuse-vulnerable, just took her until week 2 to meet someone who is. The combination of Confuse and Slow pretty much wrecks everyone I think. Confuse may fail occasionally but a slowed Piplup gets so few turns it won't matter.
Mogu (BoF1) vs Mindy (FF4): Mogu has too much more damage.
Adam (SF1) vs Hetzel (FE10): Adam can't take less than 1 damage, so dies in 32 attacks. He does 1 damage himself. This comes down to who has more HP... and FE bosses are def-over-HP, and Hetzel's HP particularly sucks (similar to Sephiran's). Adam should kill first.
Shion Uzuki (XS3 boss) vs Slime (Saga): Okay, Slime is almost as undamaging as Shiho. And slower. So it's actually less threatening to Shion offensively than Shiho was. And runs out of WP eventually, leaving it with EVEN WORSE DAMAGE which no longer drains, so Shion wins this... eventually.
Cinna (FF9) vs Big Joe (XG): Cinna's got like a 8-9HKO and a third average durability. This is terrible, but I -think- Joe is worse. I don't remember him well and he doesn't have a stat topic entry so I could be wrong.
Magikarp (RBY) vs Solt (CC): No. Solt's not THAT bad.
Pichu (GSC) vs Leon Felpool (SO2): I'd be stunned if Leon loses this. For starters I half expect he can reduce lightning in some way.
Connie (S3) vs Siegfried [Ghost Train] (FF6): Connie is apparently a bit more physically durable than I thought (over 35% pdur!) so she should tank Siegfried's opening chain, which does roughly 27%, and one extra physical since she somehow fails to OHKO. Pretty close, though.