Lotso and Facilier both have an excuse despite arguably being more heinous, they still have a more sympathetic reason.

While Facilier is the most heinous, he’s acting out of desperation and a desire for survival unlike the others. So IMO only, I’d say he’s the least evil.

Yeah, I'm sure most people would act desperately if their souls were condemned to hell.

Even if they can’t qualify since they’re a group, the Friends are arguably the most evil characters in the movie rather than Facilier. The other three are absolutely the worst characters in their work on the other hand.