Round 1: Sans. He was one-shot by
Chara who is labeled as 2-B,
Multiverse level. No wonder the guy was one-shot. Even then, he didn't die right away, he still had enough power to at least limp off the screen, THEN die. Shadow is
City level. It doesn't matter if their both in character, Shadow realistically can't hurt Sans, and because he's killed before, hence the Villain Shadow option in Shadow the Hedgehog, he's done for. Karmic Retribution could hurt Chara who is, again, 2-B. Shadow's speed isn't helping him whatsoever.
Round 2: Sans casually stomps by breathing. Yes, Super Shadow is
Multi-Solar System level, but that still isn't enough. Plus, stacking that upon the fact that this round is speed equalized, throwing Super Shadow's only advantage out the window, but also
bloodlusted Sans?! When he was REALLY ticked off, he threw Chara into the wall countless times with telekinesis. Super Shadow gets one-shot.
Round 3: Sans STILL stomps. Actually, this round is EXACTLY like Round 2. Shadow is
Multi-Solar System level, speed equalized, versus a seemingly 2-B equivalent, bloodlusted Sans.
Might I say, this is a spite thread, as Shadow stands no chance in any of the three rounds.