Here is a curiosity: I said earlier how Sonic Emitter: Tarantula from Old World Blues is an instakill weapon that will destroy everything up to and including Giant Roboscorpions, Legendary Bloatflies and Deathclaw Mothers in one hit upon scoring a critical hit. On a whim, I went on fallout wiki to check if they have that listed, and lo and behold they don't. I remember this WAS a factoid there at one point, but now they have some bullshit about this only happening with Pyromaniac and Laser Commander perks. I can tell you this is not the case as I still got instakills with low Energy Weapons skill and neither of these perks.
So, I went into GECK to confirm this.
After some testing, I found the culprit, Critical Effect listed in the tab below, at the bottom of the window

The object effect does little more than do EMP damage and create the smoke effect upon hit, which does pitiful little damage and doesn't even set the enemy on fire. The real fireworks start when the Critical Effect activates, and in order to make this work you need to set "ON DEATH" flag right next to it off so that it activates on every critical hit. I found that not every critical will activate the insta-kill effect, sometimes it will just do extra damage like you normally would and other times the weapon will kill an enemy instantly, setting them on fire and gib them into giblets. Anyways, I tested this on a brand new weapon, and the insta kill effect works fine, just like on Tarantula itself.
My point still stands, the wiki is wrong about the insta-kill effect only activating with Laser Commander and Pyromaniac, it works via a spell that activates randomly on every critical hit. The wiki, as they often are, is currently wrong, and I can't be bothered to deal with the fandom cattle to fix it myself. If nothing else, hopefully you found this educational, and now you can give this effect to any weapon you want. I don't know why people are sleeping on what is de-facto most powerful weapon in the entire game.
I am re-creating the Infinite Warfare ray guns right now, using this mod as a base
This one overrides info on base game weapons, so I don't recommend using as is, but I am making copies of these weapons so they're stand alone and don't replace vanilla/DLC weapons. I already added the Tarantula effect to a semi auto laser gun and it is amazing, I can see it being an absolute beast with an Energy Weapon high-crit build.