"Recurring" villain dies first round.
In Rime of the Frostmaiden there's a section where a gnoll vampire is supposed to be the recurring villain, hunting the 8th-9th level party then fading away in mist form the moment he takes significant damage, only to return later and trouble them again.
But the first time I ran the campaign he was barely an irritant, and this time was no different. He rolled low-ish initiative, three party members beat him, and with high damage output he was taken down before he even got to act. The scenario doesn't give him a coffin to return to, but even if he had one, he was pinned in a moonbeam and wouldn't have been able to take mist form.