Your account level must be at level 5 to play against other humans which is required for most achievements.To unlock Untouched, you must stop the enemy team from earning any points. Points are earned in various ways depending on the game mode you have selected.
Siege
The way to score points in Siege is capturing the payload, pushing the payload to the objective, and defending against a team that has initial capture.
You must capture the payload and push it all the way twice to score all 4 points and not allow the enemy to score any points
For a more detailed explanation of Siege:
*** Spoiler - click to reveal ***Both teams must try to capture a central point by filling their own meter. Neither meter will empty. The meter will fill when a team is on it and no opposing players are on it. If a meter is almost full and an opposing player contests, Overtime will start for 3 seconds, refreshing anytime they contest again. This phase can last an infinite amount of time. The team that captures this point will earn a point.
Once the control point is captured, a payload will appear. The team that captured it must have at least one player near it to move the payload. Opposing players can be near the payload to stop it. If the payload has not been pushed for a while, it will start to go backwards. If the defending team holds it for 3 minutes, they get a point, but if the attacking team push it to the end, they get a point. If the time runs out, but an attacking player gets near the payload, Overtime will start for 6 seconds, refreshing anytime they contest again, but it will eventually shorter to 1 second.
If a team has 3 points, they must capture the objective or push the payload to win. Defending against a payload will not earn them any points (not that this applies to this achievement, but it helps to know.)
Payload
The way to score points in Payload is by pushing the payload to the objective or defending against the other team when it's their turn to push the payload.
You must capture the payload and stop the enemy payload to score both points and not allow the enemy to score any points.
Survival
The way to score points in Survival is by eliminating the other team before they eliminate your team.
You must win 5 rounds in a row to score all 5 points and not allow the enemy to score any points.