I'd also chime in that the Spiritualist colossus is one of the most fun ones in the game and that it has a special function many people are not aware of. Everybody knows it makes pops spiritualistic, but what is less commonly known is that pops who are robots, gestalt drones, and biotrophies are destroyed instead. So against synth, machine, and hive empires it functions like the neutron blast (clears pops, preserves districts and buildings). It should also instantly destroy Contingency machine worlds.