The Diamond is a simple one-control compressor, wonderful tone enhancer and has useful well-designed eq.
The Empress is a full-featured compressor with a fun and useful tone switch.
Broughton Omnicomp has most of these features and has a bit of the Diamond tone.
The Fairfield Accountant is not specifically made for bass guitar but it works, it’s fun (can’t explain why I say this but it’s true) although could maybe use some tone thickening somewhere in the signal chain, really interesting dirty tone. One of these days I’ll get a Damnation Audio Dirtfixer for this and the Fairfield Barbershop.