As Breadly Weapon said, you need to win a match without blocking any attacks, in the Temple level, in Ladder mode. Here are a few things I've discovered in trying for this achievement.
- Normally, there is a priest standing at the altar performing a sacrifice. But when Noob is present, the priest is missing. So instead of looking for Noob, just check whether the priest is there. Noob is off to the side, and dark and hard to see. But you can check for the priest as soon as the stage is loaded, since he's right in the middle.
- You will not fight Noob nor activate the achievement if you win by timeout; you must take away all of your opponent's health before the time runs out. So don't set the round time limit to 30 seconds; set it to at least 60.
- You cannot get this in Tag Ladder; it has to be regular single ladder. Noob will never appear on this stage in Tag Ladder mode.