Specially the ones where you have to find stuff.
I usually attempt and manage to get them without looking up any info, but other times I miss something and I don't want to go thru the tedious process of re-combing whole sections of the levels, or even starting over, just to find some stupid note that I overlooked. Yet, I want the achievement, so I end up looking a guide and I feel like I haven't truly earned the achievent.
Yes, I know that playing a videogame shouldn't become a task and that I simply should play it the way I enjoy it the most, but I want too see what others think.
It's the same as those people yelling at others for not enjoying the sunset right. Everyone has their own way of enjoying what they enjoy, we just need to let them do it as long as it's not harmful.