For those individuals going for the One Final Firefight
achievement, the same tips apply here: easy difficulty, all skulls except Blind (unless you really want to!), and keep assassinating Elites, preferably with a sword once the generals begin to spawn.
Something I would like to note here that I haven't seen elsewhere is that this achievement seems to pop after you have died and gotten to the scoreboard after the mission ends. Don't be like me and panic that the achievement is bugged!