Rarely does one get to see a movie knowing little to nothing about it, but I was fortunate enough to get a chance to catch Headhunters, and purposefully avoided anything and everything about it. It seems a good choice. Even knowing though, that is of the thriller persuasion, the film is Norwegian, and so the tone and style is different than what most are used to, and the blood and other R-rater material may be a bit unnerving.
All that said, I do recommend Headhunters. It is a bit unusual and very memorable, and completely satisfying. I understand you will have to see The Avengers first, as well you should, but Headhunters is very worthy and pretty special. There is nothing similar in recent memory, and if you are still unsure, I have more to say.
Please check out my entire review at Scene Creek.