Campaign of Vengeance

Campaign of Vengeance is a Commander card through and through — three opponents means up to three drain triggers per attacking creature, and token-flood strategies can stack those triggers into double-digit life swings in a single combat. In one-on-one formats like Modern, Pioneer, or Legacy it produces one trigger per attacker at best, making it a slow six-mana enchantment competing against far more efficient threats; no competitive list wants it there. Oathbreaker shares the multi-opponent math of Commander but the lower starting life totals mean the drain races faster, which is a minor upside if you're building wide in that format.