Idea, when you get an ending you just go back in time to the start of the game without restarting so you just have to get all other endings to get the secret ending and final ending
also amogus ending: kill all impostors in sus town with an item that you get in the sus shop called the impostor orb (69 million coins, also shop does not close) which allows you to kill impostors, then kill them all and go to ???, then make him die (no fight starts because of the sus town fighting system and he is a crewmate) then merge the shard and portal mod with a medium machine that merges things in the lab to make a sus orb and become an amogus, you also have to get the axe and modified gun, impostor orb makes you able to vent out of the shack and into morshu's shop so then you have to kill morshu, the merge the ax and gun to make an impostor knife, then go to sus town, into the sus castle and meet lord amogus, he sends out the among drip army and then you have to fight them all, lord amogus sees you power and dethrones himself and then you become amogus.