Tenchu Z

Quite self-explaining just like the other achievements. All you need to do is get 900 points or more in 30 missions, these can be any missions and can be carried across difficulties.

The easiest way of getting 900 or more points is stealth kills, you get 100 points for normal sk's (stealth kills), 120 points for total sk's and 80 points for chokes then sk's. Patience is also key, be sure to notice enemy movements as there is always gaps for when you can strike.

You also get points for special objectives such as boss kills (sk's give you more points then normal kills) which vary depending on the boss, you'll get 100 points if you can survive the mission unharmed and another 100 points if you haven't used any weapons. If you stay undetected you get 150 points, make sure to use sk's effeciently especially from rooftops and also use your crouch when landing and moving around populated areas.

Avoid killing civileans which results in 300-400 negative points and detections which are minus 80 points each. Be sure to not stay in mayhem mode to long as well, as you'll lose minor points for that depending on how your long your in mayhem mode,