DLC in all its forms. All rationalisation and justification for it is just false-economy bullshit. Developers today just hold over 20% of the game originating from the early planning stages to charge you extra for it.
Even the idea that they're working on "extra" content post-release is a load of crap. The only difference is that they only have to complete 80% of a game by the release date and then charge you 100% of the price.
I'd tie it with always-on DRM, but you can avoid that to a point... For instance I'll only ever buy (a very short list of) Ubisoft games on console.