It's pretty much every band's nightmare to have the singer walk out on the project. Since you have to worry about the vocalist as being the mouthpiece of the band, there's no real way to recover once he decides to call it quits after having a falling out. Although that should be a sign of death for most other artists, these bands weren't going to let one dramatic diva be the end of them.
Rising like a phoenix from the ashes, these bands all found the strength and confidence to continue on without their leader, either hiring a complete unknown or picking up some decent chops of their own along the way. While most of these lineups had varying degrees of success in their day, the quality of the songs never faltered as a result, sounding just as good as experienced musicians as they did when they were young and hungry.
Hell, a switchup like this might be exactly what a band needs, stepping out of the fold and becoming more collaborative as a result. Even though there will always be naysayers who will miss the early days of these bands, these singers don't need to worry about a thing in regards to their own style. From this perspective, their legacy is already secure.
10. John Bush - Anthrax
Out of all the Big 4, bad luck seemed to follow Anthrax around wherever they want. From barely getting signed to Megaforce Records in the early days to being on tour with Metallica during Cliff Burton's death, there was no real end to the setbacks that they had to endure before seeing success. Hell, even when they got the notoriety off of albums like Among the Living, they had to cut ties with Joey Belladonna just a few years later.
After the tumultuous process of creating Persistence of Time, the creative partnership between Belladonna and Scott Ian hit a boiling point, with Ian threatening to quit the band if they didn't find a new singer. Though Joey's upper register fit in perfectly with the chaos down below, they really managed to knock it out of the park by getting John Bush at the beginning of the '90s.
Already a seasoned veteran on the metal scene with Armored Saint, Bush's heavy baritone was much better suited to the kind of music that Anthrax was putting out at the time, almost like he had a lion's roar buried inside him. Starting off with the track Only, Bush hit the ground running and never seemed to stop, staying the course and getting even heavier as time went on with records like We've Come For You All. Although Joey might be back in the band now, it's not like Anthrax were necessarily hurting during those years of absence.