Seeing lots of useful information/ videos on this thread. Thank guys. I really want to improve as Ness. Check out these matches and let me know any advice you would give
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Be careful, at 0:30, you did something extremely risk, if Pit had capitalized that, he could have gimped you with his Down B.
You're using PK thunder onstage at moments you shouldn't be using it and is being punished for it. The only times you should use it onstage is if your opponent is above you so you can juggle him or as an edgeguard tool. If you want to do something risky but with very high reward, you can PK thunder while your opponent is really close to you. He will be hit with the hitbox from the frames when pk thunder doesn't disappear and you can try to PK thunder 2 his face.
I also noticed you're not punishing the other player properly. I saw a lot of opportunities being wasted because you either tried to Fsmash him, dash attacked his shield or rolled away from him.
You're wasting good edgeguard opportunities, examples of that are in 0:08, 0:16 and 2:56.
I didn't saw you using PSI magnet to absorb Pit's arrows. You don't need to be afraid of doing that because you can use Magnet cancel, a Ness' AT that let's you cancel PSI magnet into a Jump, a backwards roll or a spotdodge if you do it right after absorving a projectile.