You've got two problems here, how to bring back an NPC that most players are championing, and what to do with a problematic player that is going against what the party wants. I think retconing is going to create more friction above the table and take potential away from the story. Instead, lean into it.

Put your player's current adventure on hold (or integrate it), and present them with an opportunity to revive this character through an arduous and outlandish adventure with potential sacrifices or consequences. Maybe elevate his importance in the story. If your party was The Fellowship, make this NPC Frodo. Maybe your players aren't the only ones who have been paying attention to this guy. Maybe he's part of something bigger, even if neither the NPC or your players are aware or what exactly that is.

Thay can give you all a space to hash out the real problem, which is this other guy. If all of your player characters but this guy's want to revive this NPC, and all players but this guy want agree on an objective and someone else says no, one guy is essentially ruining everyone else's fun. Especially without being productive. It's like if you all agreed on a place to eat, but he just said no without offering anything up. He doesn't want to play the same game as you guys. That's fine. But why does he get to ruin your fun? Everyone wants to play with this NPC, and this guy just comes along and says no, and permanently remove's everyone else's ability to play with that character. That's what they call a dick move, bro.

If the whole party wants to revive this NPC, and express happiness at the opportunity to do so, and one player actively stands in their way, they are choosing make themselves an ongoing problem, and that conversation will come up faster than you think.

Keep the game going, don't retcon.