Continuing the discussion from Why is valiant ability so hard to unlock?:
As a reminder, Valiant is unlocked via reaching r12 on any map with coward equipped, without taking any damage.
Choose mystic library, then summoner, as a coward ability(/ability coward).
For singleplayer:
Stay far away from zombies to avoid damage.
Try to get blade staff, dark harvest, and dragon before round 5.
Save up for terraspark, then the rainbow crystal staff.
When you hit round 11, camp from the sniper dudes.
With practice you can unlock valiant.
For two players:
Open the top left room by playing normally. Then, let the lobby die and repick the map.
Have the person unlocking valiant select coward and sit in the room. The other should just play normally
For greater ease, use a tank sentry to draw aggro to the middle. Same as before, the final aim is to upgrade the rainbow crystal staff. The only difference from singleplayer is that the second player can grind points freely, making it easier to reach r12.