The worst DLC I have seen was "Ranger Mode" for Metro: Last Light.
$5 for a higher difficulty level. Advertised as "the way it was meant to be played".

It should be a felony to pimp DLC in that manner.

Late reply, but ah well.
I don't know if there was a five party member mod. There is a mod to take the dog as a 5th companion though.

Well better than nothing. I always wanted the Dog to tag along.

...You are talking about Freeware games, right? :D

DLC so bad, it's awesome:
Tour De France 2011 - Power Up
"This additional content offers an energy supply pack for use with your riders during races in order to improve their performance!"
Does anybody else feel weird when they read this in the context of this particular game? Admittedly the German description I read a few years ago sounded even more like the developers were trying to sell me drugs.

Anyway, generally the worst DLC there is are consumables (I'm not sure Tour de France's Doping Pack™ is one of those) or XP/currency boosts. I've bought all sorts of crap for games but something I'm never going to pay for is stuff that that will just save me game time or that is going to pull off a Jimmy Hoffa after pressing a button. Even costumes, hats and hair styles have infinitely more value than this kind of crap.

Game patches might be included as well. Patches do often contain game content, and for the most part throughout gaming history they have been delivered without charge.

Demos, too. Remember those? Demos usually contained large portions of the game itself, with just enough pieces missing to lure the consumer to make a purchase.

Expansion pack 1-x years after games release is a good thing, but every dlc in the first year or at least already finished in the same year as the game was sold is a shameless cash grab and is one of the reasons I stopped buying new games for many years with few exceptions.

Not always. Sometimes it's because developers keep working on and improving the game.