this is best done with two point swing as well.
Have one person from Gold team go and capture the enemy flag and after capture kill at least two of the people from blue team (this depends on the number of people you have on each team) Then some one from blue team take the gold teams flag, (again depending on how many people you have you may have to wait for someone to respawn to take the gold teams flag.) The gold team member with the flag then kills the blue team member with the flag and then recovers flag and scores. Repeat as needed for each member of the session.
2 Achievements with one whack