An Artist's Pinnacle

We've had so many threads about favorite releases by an artist, best debut recordings etc., but I'm don't think that I have seen anyone ask this before. My question is this: Pick one or more solo artists, or bands or music from any genre. What release do you think marked the pinnacle of their artistry?
I could think of many, but the idea was sparked in my mind yesterday when I was thinking once again that for REM, it was Life's Rich Pageant. They were once a favorite band, but I eventually got really tired of Michael Stipe's nonsense. Anyway, that's not the point. Continuing with the rock genre, I will say Dirt was the peak for Alice in Chains, and Rocks was the top for Aerosmith. Only thinking of those examples because I was just listening to them yesterday.
I'm really interested in everyone else's thoughts, and I'll have a whole lot more as I think about it.