Stellaris suggestion: Endwar

Once you get to the lategame, it's quite tedious declaring down the rest of the galaxy, they all tend to end up in a Federation anyway, making it irritating to take all their worlds. On 1000 star galaxies it becomes incredibly boring, waiting for the truces to end, declaring the next war and so on.

My suggestion is to allow the player to declare Endwar, which declares war on every other empire in the game immediately. In essence the player becomes a crisis, getting a bonus to mineral production, ship build speed and naval capacity, while all AI's work together to fight the player.

Instead of the usual capture planet mechanics, the player immediately owns and controls the planets they land on, either enslaving the population or purging them with +100% speed. The player also gets the option of razing the planet slowly, yielding large amounts of minerals and energy but destroying all pops and structures and turning the planet barren. If the war goes poorly, the same can happen to the player that declared Endwar.

This might also be useful when the End of the Cycle occurs, as a way to speed up the war declaration.

It makes sense for a fanatic purifier, once they've seen off the FE's and crises to declare war on the rest of the galaxy and abandon the restraints of truces.