yeah I meant imperialist as a play stile more than a specific combo.
some more examples from this game: after a couple more war I split the fanatic purifier enar to me, half was the status quo friendly empire, half was later conquered and vassalized by me for no reason at all.
I federated with the friendly empire, good. then went to my parent empire to get him into the federation, but no, he hated the gut off my vassal. fine, I left the federation, liberated the vassal, federated again with the dude below and then discovered dude below was vetoing me from joining with the parent civ. fine, I left that federation, waged a liberation war with a militarist on the other side, entered a federation with him and the liberated vassal. then went to the first liberated civ but no, now they hated the small ex vassal that was no biggie before. fine, left the other federation, joined the first liberated dude and then realize ex vassal + new liberated were still in a federation. so I went on another war with the whole federation, vassallized the dude, freed him, and before I could send a federation request to the new liberated empire they decided to subjugated under another empire.
now it would have made for a great story, if it were not a multiplayer game. federating my neighborhood was the only way to stop my friend playing your bog standard imperialist, and while I was literally wrestling game mechanics and its -1000 modifiers with no logic behind, he was just gobbing up other empire capitals and their precious pops.
I managed somehow to maintain technical and naval parity, but when the border clashed I could only resist so far against his overwhelming economy - using carrier against his citadel, corvettes against his cruiser and battleship fleet, all the trick I could, but he could simply sit forever on the front spamming ships and I could not keep up losses on the front long enough for forcing a truce
now, I've done my fair share of mistakes, but most of them were just game mechanics being obtuse, and that's not a nice way to go.