I got this easiest on objective based gametypes. Like Retrieval, Domination, and Detonation. Wait till the enemy is slowed by a canister, stopped at a CP, or planting a bomb. Chuck a digi followed by a frag grenade. They should explode one after another, first causing them to be effected by a Digital Grenade, then killing them with the frag.
If you hold the bumper your throw will be delayed, allowing you to time throws better, giving them little time to escape.
Have a friend on another team meet you at a secluded location, one unfrequented by most.
Digi your friend, then kill them.
Rinse and Repeat either method 10 times and you'll have this easily. Just be patient.
There has been some confusion as to whether the 10 kills must be done within one match. And the answer is no. They don't have to be done in one match. They can be obtained through as many matches as it takes.