SWTOR, because of the amount of paywalls.
I generally really don't criticise against F2P games though, mainly because, they're free, you have the option to pay or not.
A game that is currently annoying me is HearthStone, you can slowly earn a single booster, or pay for a whole bunch of them, making a somewhat weaker experience for the financially difficult players. It's a great game, but in that regard of fairness it can be annoying at times.
That being said, I also play Magic the Gathering, so I should be used to this.
*sips tea*