So to begin, let's start with Lord Garmadon.
Garmadon is a moderately heavy character with slightly above average speed and good attack power.
He possesses a "meter mechanic," as I like to call it, where he slowly finds his True Potential. The meter slowly increases every time Garmadon takes or deals damage, referencing the fact that it's the "fight that fuels him." When the meter is full, Garmadon's True Potential activates, giving his attacks a significant power boost. The boost lasts for about 20 seconds and while it does gradually weaken over time, it can't be depleted by attacking him like it can with other characters like Little Mac and Cloud. The meter also depletes completely if Garmadon is KO'ed.
Now for Garmadon's special moves:
For Garmadon's neutral special, he can fire the purple energy blasts he has in the show. They work in a similar manner to Fox and Falco's lasers.
His side special has him attack using Spinjitzu. While it's an awful horizontal recovery, it works quite well on stage, as it can strike multiple times and the hits connect fairly well, leading to good damage output.
For his up special, Garmadon launches himself up using a blast of dark energy. Yeah, I REALLY had to stretch for Garmadon's up special as there was nothing I could think of for it. If you have any suggestions as to what it could have been, tell me.
His down special is a counter similar to that of Arsene Joker and Palutena. If the opponent attacks up close, Garmadon uses the swords he made with his powers to fight Lloyd and Wu in "Green Destiny" to block said opponent's attack and then retaliate with a powerful slash. If attacked by a projectile, Garmadon creates a shield with his powers to reflect it back at the opponent.
Final Smash: Oni Titan:
Garmadon summons his Oni Titan to wreak havoc on the fighters.
Garmadon's alternate costumes:
Garmadon's default design is his current design in the show. It can also be worn with his color scheme in the LEGO Ninjago Movie, Mr. E's color scheme, or in white and gold. Garmadon can also wear his outfit from the LEGO Ninjago Movie, which is available in it's normal design, with the show Garmadon's color scheme, in red and blue, and in silver and white.
Either way, that's Garmadon in Smash. Again, I am not LEGO or Nintendo, and therefore I don't own Ninjago or Smash Bros. If you have suggestions for who to do next, tell me, and let me know what you think of my take on Garmadon in Smash by reviewing.