So I've played a few matches online and I'm just getting destroyed. I'm playing as Suicune. What is the best way to practice so that I'm not so terrible. (Mewtwo is just so fast I don't feel that I can do anything to beat him).
In Field Phase, Suicune's down Y is chargeable and forms a crystal wall in front of it. This wall can block so weak projectiles and can force the opponent to approach from the side, I personally like to play with how it blocks perspective and hit people with a surprise Aurora Beam.
If you played the tutorial, then you already know Poké Combos are your go to attacks in Duel Phase especially for beginners. You probably already guessed that Suicune is at it's best when thee is some distance between it and the opponent, so make sure you have that distance when using Hydro Pump since it has a bit of a charge time and leaves you open. Aurora Beam comes out quick and can be angled upward to shoot diagonally, compared to Hydro Pump, it is a little more difficult to approach from it, but it still leaves you open if you are close enough.
Suicune's midair A, Blizzard, is a bit tricky for some characters to counter on block, since it pushes back when Suicune falls to the ground and you recover quicker than most would expect, your opponent might try to attack right away, so it would be a good idea to jump out of it.
If you need to put some distance between you, Suicune's midair Y is pretty good, since it's effective when jumping backwards, there is also it's counter attack, which has a follow up if you press Y when it hits. Aerial opponents can get hit by the angled Aurora Beam or standing X (directly in front of Suicune) and forward X (about half way across the screen). Hail right after they get up, can block some approach, combined with Icy Wind (hold A then release) can force them to block, giving you some breathing room.
If you are fighting someone who uses projectiles often, Mirror Coat would help in Field and Duel Phase, since Suicune will counter with Hydro Pump, this works with attacks from supports like Frogidier too.