Minimum player count necessary for co-op

So i've been scouting guides and stuff but can't find this info anywhere. How many players do i need to finish every multiplayer and co-op achievement? Can it be done with just 2 players?

Also in unrelated news, i'm looking for a dedicated, patient co-op partner to finish said achievements. Anyone interested, message me on XBL

You only need 2 for most of the stuff and I think maybe 3 for one or two things (might not, it has been a while). When it comes to the challenges just go with 2 on most, but some are far easier solo due to the nature of the score you get in solo vs co-op

Ok! Thanks for the info, very helpful!

I need a boosting partner