Go to "Multiplayer", then "Public Match" and create your own game. Set the maximum number of players to 14 and reserved slots to 13, then set the game to first 5 out of 9. Place bot players on the opposite team and be the only player on yours. Begin a match on the Buffalo Field. Eliminate as many players as possible, then let the final person shoot you. When they have won four, stay put and win the last five by taking out all the players. Rush straight to the right and the opposite team will line up on the opposite end. Continue shooting them and making new games with the same rules until you get the achievement.
ACHIEVEMENT - HOW TO UNLOCK Amateur Paintballer (150 points) - Beat Career on Amateur difficulty level. Semi-Pro Paintballer (150 points) - Beat Career on Semi-Pro difficulty level. Pro Paintballer (200 points) - Beat Career on Pro difficulty level. World Tour (80 points) - Play a game of paintball in all the Career and Woodsball locations. Training Buff (30 points) - Complete all training stages. Communication Skill Proficency (50 points) - Max out the main character's Communication Skill. Handling Skill Proficency (40 points) - Max out the main character's Marker Skill. Reload Skill Proficency (40 points) - Max out the main character's Reload Skill. Speed Skill Proficency (40 points) - Max out the main character's Speed Skill. Accuracy Skill Proficency (40 points) - Max out the main character's Accuracy Skill. Woodsball Chief (50 points) - Win 50 Woodsball Ranked Matches over Xbox LIVE. Speedball Chief (50 points) - Win 50 Speedball Ranked Matches over Xbox LIVE. Predator (80 points) - Make 200 eliminations in multiplayer matches.