What is the largest speedrun battle you know of. (Multiple people fighting for a world record by a few frames) Mine is: https://www.speedrun.com/nr_ninja_steve

Super Mario Bros and Mario Kart 64 come to mind.

currently, there are a few interesting races going on for several classic NES/SNES games. Right now, there are 4 people grinding for 4:54 in smb1 any%, 4 people grinding for a 35:XX in TLL D4 warpless, and 3 people grinding for an 11:19 in castlevania.

CV quest for 11:19 https://multistre.am/sbdwolf/evadecaptcha/kissmyafrocard/layout6/ SMB1 quest for 4:54 https://multistre.am/lekukie/miniland333/niftski/thelxinoe/layout11/ TLL quest for 35 https://multistre.am/kosmic/adamferrari64/andrewg/superboomfan/layout6/

I'm not sure if there are any other games with fierce competition coming from more than a few runners, but these are the only ones I'm following