Pathfinder 1e Bestiary 2     Pathfinder (no source link)
Monsters Of The Underworld     D&D 5e original/official source
Monstrous Manual: Dragonlance     D&D 2e (no source link)
Scruffy Grognard's Monstrous Manual     D&D 2e (no source link)
Hacklopedia Of Beasts     Hackmaster (no source link)
Monsters Compendium     Heroes Of Adventure (no source link)
The Monster Overhaul     OSR (no source link)
Lairs And Encounters     Adventurer, Conqueror, King (no source link)