Dark Sector

The Glaive is a pretty badass weapon from the start but the ability 'Power Throw' takes it to another level. You will unlock Power Throw through natural story progression a few minutes into Chapter 3 - The Baggage Claim.

Now instead of just pressing RB to thow your Glaive hold down RB until your reticle turns yellow and then release to perform a Power-throw. It might take you a few tries to get the timing down but you should be able to figure it out rather quickly. It deals 4x the damage as a regular throw and is usually a one-hit kill on regular soldiers and other generic enemies.

Now simply kill 30 enemies throughout the course of the campaign and the achievement is yours. Make sure to get it in 1 playthrough as I cannot confirm whether the counter adds up or resets when starting a 'New Game+'. Unfortunately there's no visible in-game counter but if you concentrate on Power Throw's you can get this easily as early as Chapter 4.

In addition I would recommend aiming for the head to kill two birds with one stone and gain progress towards the 'Headhunter' achievement. Later on you can also combine Power Throw with the 'Aftertouch' ability to gain progress on another achievement called 'Finesse' but you'll figure that out as you continue through the story.

Good luck!