H4 M4 LASO Deathless - Why don't these melees kill?

Halo 4 Reclaimer, how to get caught and exit invisible barrier in route to force field.

hatred

Rubber Plasma Nade

Deathless run ends, unfortunate Dynamo throw cost me

Deathless run ends, forgot about that Grunt

Defective Plasma nade?

Deathless run ends, Grunts in the bushes

Deathless run ends, distant unseen Jackal somehow snipes me in the back