[quote name='metaly']For people trying to get all the achievements, I'd guess that it takes at least three playthroughs. You need to do:
1) Three complete games with a different squad each time for the ally achievements
2) A game each as a soldier, adept and engineer for ability/weapon achievements
3) One game on Normal, Hardcore, and Insanity
So mix and match those, do a game each as full renegade and paragon (if you're not using the glitch), and make sure you pick up the miscellaneous stuff like Completionist, Scholar, etc. along the way. If you only care about the achievements you can probably just keep reloading a save file to grind out weapon kills/ability uses since they're cumulative (thereby skipping #2 on the list), but where's the fun in that?
You'll also probably have to replay a character at least once in order to get to level 60. I did a complete game and got to maybe level 52, and then reused the character for a missions-only (for the most part) Insanity game and was still ~100k away from 60 by the very end, so you can probably hit 60 in two games if you're thorough.[/quote]
So can I switch to an engineer on my next play through? I'm a soldier now. Also, what do you mean that the weapon kills/ability uses are cumulative? Are you saying I can load a save, kill 5 things, reload the same save, kill the same 5 things and the game will think I've made 10 kills?