Highly subjective. What does "their potential" mean? I'll leave that up to you.

What prompted this? I was thinking about The Walkmen. They seemed like a band who could conquer the world. A great mix of commercially-viable sounds but with the ability to do esoteric stuff like covering Harry Nilsson's Pussy Cats.

Listening to Bloc Party who were hugely a buzz-worthy band and thinking about how they just disintegrated.

I'll give you Bloc Party. A pretty great debut album then a lot of mediocrity.

But, damn, I'm not sure what more you wanted from the Walkmen. Eight very good to great albums, the worst of which was that cover album. That's a pretty nice run for a band, especially in this century. I think they reached their potential and more. But like you said potential is pretty subjective.

First band that comes to mind is TV on the Radio. Very unique sound, and I like their work a lot, but I kept expecting them to be better.

Agreed re: TVOTR

Their first EP and three albums are unbelievably great. Their last two albums----not so good. Crickets since 2014. Too bad.

I friggin' love the song "Happy Idiot" on TVOTR's last (2104) album (Seeds). But yeah...they could have been so much more popular.

Some bands that I enjoyed that I thought could have been more popular or made better albums are: Longwave (great first album was great, the 2nd one good, and then...), The Music (I blame their terrible name for making them hard to find or discuss), The Rakes (Really liked their first EP and one of their other albums, but I don't think they could ever make more than the one song that sounded like the rest of their songs), The Bravery, and The Sun (what a nice fun band that just kind of disappeared, also a terrible name).

I was going to include Editors, but it looks like they have had some popular tunes outside of their debut. I just never heard of them after "The Back Room."

Johnny Taint n' teh Cans of Piss.

Though I do like their cover of "Cocaine". (Find it on YouTube under 'world's worst cover band plays Cocaine'. Love that LOOGAR went for it & wore the baldcap & mullet combo to really make it pop. Busty Rhodes did literally nothing on the bass, though, & SSSQQQUUUIIIRRRGGGLLLEEE hid back on guitar & let BLOOR get that guitar solo shine.)

Also,

SATELLITES.

As promised (?) Johnny Taint n' teh Cans of Piss performing the J.J. Cale via Eric Clapton classic, "Cocaine".

The Left Banke