i dont know if what i'm puttin' is on here already or not, but i'm not reading 11 pages to make sure. but anywho here are some tips:
-if you have the smash ball and your opponent is at high damage(90+), instead of using the final smash, KO them, knock there damage meter to 50%+ when they come back, then use it.(do this if you are sure you wont lose it)
-bystanders get hurt by the slash, you all know that, but just in case y'all dont know this, this includes your teammates if done in a team battle, so metaknight's final smash can hurt both opponents and teammates(kind of sad). so if metaknight in a team battle, warn your buddy about when to dodge so you dont screw him up.
-never forget that all of his special moves can be useful for recovery uses. just figure out which ones are best in a certain situation
that's all for now. i may do more in the future, so keep a look out.(note that i'm not a noob in smash, i just never post stuff here)