A7X springs to mind. Their first album (Sounding the Seventh Trumpet) wasn’t great, but once Synyster Gates and Johnny Christ came into the fold, the band has put out a very consistent discography. Every album has its own distinct style, and even if they head in a direction that I don’t necessarily love (Hail to the King), there’s always something for me to latch onto musically and I know that the next album will be completely different. Plus, they’re one of the few bands that takes fan criticism into account and admit to mistakes. Their newest song, Mad Hatter, was criticized for its mix, and the band relistened to the song and fixed it. I don’t know of many other bands, if any, that will do that.
The only other bands that I have almost full trust in are Dream Theater, Halestorm, and Haken. Most of my favorite bands have had enough slip ups that I can’t be completely sure if I’m gonna like what they do.