How about Sublime? I’m not a huge fan, but I heard a Sublime song on the radio and thought of this thread. Their third eponymously titled album was a huge hit, with several singles that got played on the radio ad nauseum, so it could be considered their best. And the lead singer went and killed himself from a heroin overdose a couple months before its release, ensuring it would be their last.
Nah; that’s a valid reason for a last album happen.
I’m confused: did all the Pogues die? 
How about Dire Straits? Their last album, “Brothers in Arms,” was by far their most popular, and spawned several hit singles.
There was On Every Street which came out six years later, in 1991.
If we’re going by what I think is their best:
Judas Priest’s Firepower has to be up there. When that came out I could not stop listening to it, and I’ve been into Priest for almost 30 years.
Dee Snider’s Leave a Scar came out this year, and it’s his best solo stuff.
Golden Earring’s Tits ‘n’ Ass is a solid album. I don’t really have a ‘best’ album by them, but this one is solid.
Excellent submission. I was a huge Screaming Trees fan and Dust is still their highlight: Beautiful and haunting.
Relatedly, way back before there was the internet, I used to make music purchasing decisions based on the college radio station. Back then, I could afford a couple tapes a month (yes, I was still buying tapes because I couldn’t afford a CD player - late 80s/early 90s) and looked forward to the little catalog included with the tape which then led me to more music. I bought so many SST Records tapes because of that little insert. Still some of my favorite music.
Ah, yes. A very… sublime… answer.
Fuck.
Not even a mention of David Bowie and Blackstar?
Oh, didn’t now that. A lot of bands regrouped five to ten years after breaking up, for a reunion album (usually lame), then disbanded again for good.
The next band that does this should name that album “Jordan and the Wizards.”