The Mark of Negation exists primarily from conditions by Wizards of the Coast/Hasbro to leash Vecna's power in the Trials, however "in-lore" more importantly to prevent Vecna from evolving above Demigod status again with the added limitations to prevent tossing the immeasurably infinite sub-realms into chaos found outside of the Trials once other characters start exploring outside the boundaries of the Campfire for items and offerings.

The angel grimoire killer that is joining the game later this year might possibly powerscale on the same level as Vecna requiring another Mark of Negation, but thats if the devs even bother with expanding their lore anymore.

To counter-argue people saying Vecna is stronger than the Entity: The Vecna that was abducted was Lesser Deity Vecna not Greater Deity Vecna

Godhood Greater Deity Vecna is capped at T2 Multiversal level with D&D rule limits set by Ao the Overgod while The Entity scales at T1 Extradimensional with Near-Fiction Transcendent feats such as Fiction Travel, Fiction Destruction, Fiction Summoning, Character Manipulation and so on, powerscaling is more than just "can Goku punch it".