Me and most of the people I know have this same problem, when people reset or touch a killbrick, they'll respawn on my client's side, but when I kill them with my weapon, they'll simply stay dead. I have tried it with other frameworks/tools and this still happens
You are executing on the Client. Use a Remote Event, or even a script.
Killing a player with a LocalScript will not be replicated onto the server. Meaning it never happened!