I have experienced this in alot of my games recently and I have basically started to avoid getting DLC for certain games because of it. Here are some of the worst types of DLC you can come across.
Costumes: Culprits: Mostly fighting games: No doubt about it when I think of worst case scenarios fighting games want to suck out your money more than anything. I mean how many different types of costumes can you access on Street Fighter,DOA5,Street Fighter X Tekken,Mortal Kombat and various other types of fighters. They don't advance your abilities or anything or make you better they are just for show.
Character Skins: Culprits Mostly shooters: There are many character skins you come across in various games but rarely do you find them most in shooters. I mean I play Uncharted and I see lots of people going for skeleton like skins and such. I don't think this enhances the performance but it certainly isn't needed. I have heard that in Lara Croft and the Guardian of Light you get a Kane and Lynch skin to buy. Kane and Lynch who'd be sad enough to buy that.
Buying Soccer/Football players: Culprit Fifa Ultimate Team: This is just daylight robbery basically. You start out with a bunch of nobodys and you have to win with them online to get the best players in the market because your coin count goes up by playing matches and winning them. Or wait a minute let's throw it in so you have to spend either Microsoft Points or Playstation Store money to get better players quickly. EA are the worst by far and this proves. Some players must play games like this 24/7 to get the best that money can buy.
Weapon Mods: Cultprits Various shooters: There are plenty of shooters out there that people play none stop to become gods on to get the best items in the bussiness. Weapon Modifactions is obviously the most broken giving you better accuracy,damage and of course ammo. It can break games sometimes.
Adding Extra stages,tracks or characters: Various Games: This comes from various games such as fighters who didn't have the time to throw in a certain character in because they had to bring the game out quickly, Stages because they were probably still working on it and with not many stages in a game to begin with had to be thrown in at the last minute and the final one tracks from racing games that weren't finished or added for various reasons.
There are some good DLCs that have been worth it but these are the ones that can suck money out of your wallet. Be very careful what you spend you Playstation Store/Microsoft Points on. If you wish to add anymore than please do mention in the comments section below.
The worst types of DLC add-ons are the kinds in competitive games that give a person an edge, just because they paid some extra money. I can't stand that. You mention this, and it certainly does break games.
Games like Fallout 3/New Vegas, Alan Wake, Katamari Damacy, and Left 4 Dead (2) have done dlc very well, utilizing them more as 'expansion packs' instead of 'add-ons.'
@Blueresident87 At the same time, those are great for single-player games since it helps enhance the experience. DLC should be something you decide to purchase on your own. If you want to buy the DLC, go ahead.