I am currently rank one on the @_megaweapon_
$DEGEN leaderboard, and top five on the high score leaderboard.
I see a lot of people struggling to reach high scores. Here's a quick guide/strategy and gameplay video on playing the ninja megaweapon.
Phase 1: When the game starts and you aren't yet a megaweapon, mostly just ignore the bots and other players. Your focus should be grabbing and turning in the green blocks at a helipad. Obviously you still want to kill them as necessary, but dont focus on your KDA.
Phase 2: When you become the ninja megaweapon, you'll want to play a hit and run style. The ninja has a stamina bar that also acts as a damage shield. If your stamina bar is gone, you are insanely squishy. So find a remote area of the map, preferably near a respawn point, kill an enemy or two and then retreat while the shield respawns. You want to avoid big groups where they can burst you down quickly with combined damage. On maps where there are houses, you can jump onto roofs to recharge your shield and be relatively safe.
Phase 3: After you die as the megaweapon, simply repeat the above as time allows. When the game timer gets low, become more aggressive. You dont get bonus points for ending the game as the ninja, so when the clock winds down, take more risks to stack your killstreak. You will see me getting more reckless near the end of the video.
Enjoy!