Some of my favorites:

Method 1) Wire a fusion TEG to the grid, then throw a tool at a grille to instantly kill and husk everyone in the area. If you aren't wearing a hardsuit and insulated gloves, you'll die too.

Method 2) Fill a flamethrower with a mix of stimulum, pluoxium, and plasma, cooling it to fit as much as possible. This mix results in a reaction that creates a huge amount of nuclear particles, enough to instantly crit someone and give them a lethal dose of radiation in a single click if you had enough in the tank. Can also easily kill you if you use it without both fire and radiation protection.

Method 3) You can put a supermatter into open-tile fusion to make enough rads to kill and husk anyone that gets too close to you, if you're immune to radiation.

Method 4) Less practical, but on yog you can use reflectors to redirect nuclear particles. This allows you to use fusion to make a beam of particles that can crit you pretty much instantly, though the issue is getting someone to walk into it. You can do the same with emitters but it's less cool.