Disproportionate Retribution is, according to the playing with page, "A character who has been slighted by another plots revenge which is out of proportion to the original slight". Karma Overdose is "The time has come for the Big Bad (or Jerkass or just whoever's in the wrong in the moment) to get their karma. However, the punishment is so bad that the audience (and potentially the characters in-universe) feel sorry for them."
My understanding is that Karma Overdose is a YMMV trope, and relies on the audience feeling sorry for the character in question, while Disproportionate Retribution assesses only what happened in the story, without looking at the reactions of any audience member. If this is the case, we need to add something to the description to specify this, and explicitly compare contrast this with Disproportionate Retribution. We need more than "Can overlap with Disproportionate Retribution".
Tagging the two most prominent editors of this page: @GalaxySagi777 @Jlaw