Ill start with the firefight acheivements these arnt hard
1. get 40,000 total score across the entire party
2. get 200,00 total score across the entire party
3. get 1,000,000 score across the entire party, this one will take a bit of time well about 4-5 hours if your doing it on easy mode.
1. and 2. can be done in a few hours , me,gixer,icce and lib did this tuesdsay night but it was late on so we didn`t keep going for the 1,000,000, .
but we did notice if a team member kills you 3 times you now get the option to boot them everytime after the 3rd betrayal while in firefight.