Forget Fallout 76 – GenghisKhanX’s latest Fallout 4 mod, Spawn Grenade, adds “baseball-like” grenades which generate up to 50 enemies into one place.
The spawn grenade can create a wide variety of enemies, as below:
Animals – Bloatfly, Bloodbug, Dog, Mirelurk, Molerat, Radroach, Radstag.
Robots – Assaultron, Mr. Gutsy, Mr. Handy, Protectron, Sentry Bot
Enemies – Feral Ghoul, Glowing One, Raider, Supermutant, Synth
Gangs – Brotherhood, Brotherhood Power Armor, Children of Atom, Scavenger, Gunner, Triggermen
Monsters – Deathclaw, Behemoth, Mirelurk Queen, Radscorpion, Stingwing
Enemies can be spawned in batches of 1, 5, 10, 25, or 50 at once. As a bonus, the enemies spawned will fight each other if they are opposing factions, so you could create a war between the Brotherhood and the Ferals.
You can download the Spawn Grenade mode from Nexus.