pokemon 1st gen card prices Charizard [1st Edition] #4 | Base Set Retreat Cost 25 Most Valuable First Edition

With this info, I compiled a list in which I believe is in order of set release and then by card number

With Blightbelly Rat thrown in the mix youd kill your opponent in 10 turns with poison damage (because of toxic 1) and combat damage (because the creature has 2 power)

This is particularly powerful because it is difficult to interact with and can seize games even from positions where a player is far behind (indeed, it can sometimes be actually easier to win from bad positions, as boards like multiple Unholy Annex es or an Abhorrent Oculus turn to your opponent's disadvantage against Excruciator)

Things like Massacre Wurm or Sheoldred, Whispering One come to mind

It also has an odd form of mild evasion