Get a killing blow as Ashe on an enemy knocked into the air by B.O.B. in Quick or Competitive Play.
Not too hard to be honest. Once B.O.B. is summoned he will charge forward and lift the first group of enemies he sees. But here are a few tricks and things to take into consideration.
-I've seen that to fill your ultimate meter faster, rather than staying far and dealing damage, the best way is to do
damage with the dinamite, even more if you
make it explode. I was able to get about 30% of my ult in 1 play when I shot the dinamite and got 4 enemies with it.
-B.O.B. will be summoned behind you and drop a couple meters in front of you before he starts charging.
-You only have 1 chance to lift your enemies. Once he start charging he will either:
--a)Stop once he gets far enough and start attacking.
--b)Crash againt a wall or object and start attacking.
--c) Hit an enemy and lift him.
As with all other achievements, try to ambush the healer from behind or a low health character. Avoid any hero with an escape move or shield
because B.O.B. will not stun the enemy!, so any escape move can be used almost instantly. (D.Va, Tracer, Zarya, Reaper, Ana, etc.).
The lift doesn't do much damage either, so most likely after you lift them you will have to shoot them more than once, (eg. my case a McCree, I had to shoot him twice, without ADS).
As pointed out by smakzillaa,Getting hit by B.O.B. and lifted in the air deals 120 hp, which is why two non-ADS shots to the body was needed for the McCree (Non-ADS shots do 40hp)
Also, any damage boost is your friend. :)
Good Luck and remember,
Timing is Everything