Star Trek Captains in order of how fast they kill Tuvix:
1. Archer (does not feel bad)
2. Burnham (feels a Little Bad)
3. Janeway (we personally witnessed the devastation in them big ol I Had to Kill Somebody eyes, but she recovers quickly due to personal love of Tuvok and Neelix)
4. Sisko (spends awhile confirming every single possible alternative, does Not Feel Bad except when Tuvix directly calls him murderer)
5. Kirk (tries to Kobayashi Maru it. Dealer’s choice on if this results in a Tuvix AND Neelix and Tuvok live, or if it becomes one of those things that he carries foreverrr)
6. Picard (this could be a two parter episode with how much he would need to soliloquize on identity and the rights of the individual and the authority limits of a captain. But yeah, he’s killing Tuvix).
This doesn’t even touch on how the non-Janeway captains would react if their Tuvix was ALSO made up of one half Their Best Friend and Moral Compass.