Neogenic Nightmare Chapter 1: The Insidious Six - S2-E1
Stupidity: When the Kingpin is breaking all of the supervillains out of prison, Shocker, Scorpion and Mysterio all have their costumes, weapons and gadgets conveniently stored at the prison, which makes their escape easier. Surely a prison wouldn't keep superpowered weapons and costumes in the same place where the inmates are being held. They would be stored in a federal evidence locker.
Answer: All Stars #17?
Based on my Google search results, "All-Star Batman" is a more recent publication. The year I read the book in question was probably 1993, so it was probably published in the late 80s or early 90s.
Phaneron ★
I believe the answer should have been DC Super-Stars #17. That issue features the death of the Earth Two Selina Kyle as part of the origin story of her daughter, Helena Kyle (The Huntress).
BaconIsMyBFF
Someone on Reddit guessed it was Batman Annual 15 (Armageddon 2001), and based on the panels that are pictured on the website of the link they provided, it appears to be that one.
Phaneron ★
That's not it either, unfortunately. I specifically remember Killer Croc being in this, because it was the first time I ever heard of him, and he didn't debut until 1983, six years after DC Superstars #17. I think Batman killed Joker at the end out of revenge for Catwoman. With so many other characters being killed in it, I'm pretty certain it was an Elseworld story and not connected to whatever the main DC universe is or was at the time.
Phaneron ★