Melee a Bouncer to death.

Clear the first mission.

Shot a Warning Beacon

Kill 10 or more enemies with a single explosion (Tonkor, etc)

Complete any 5 Hive Infestation missions.

Polarize a Weapon, Sentinel, Kubrow, or Warframe

Score a kill with your equipped primary, secondary and melee weapons in 5 seconds or less.

Destroy 200 Corpus Crewman helmets.

Complete The War Within Quest

Complete a Hijack mission without allowing the payload to travel backwards.

Solve 10 Ciphers.

Complete an Interception node and extract with the enemy capturing 40% or less territory.