Wow, Titanium. That's an elite line up you got there. Hahaha.
Oh yeah, nothing but the best
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Between them all I have a whole character though!
Actually, Jiggs is pretty good. Unfortunately, the three other mains I have all have issues - Yoshi is great, other than not having a triple jump and being unable to jump out of his shield. Pichu is fast, but is light and hurts himself, and his kill moves are generally inconvenient. And Mewtwo has wonderful recovery and pretty good mobility, but kind of sucks when it comes to the whole "attacking" thing. But hey...
Part of the reason I have terrible mains was because I was worried I was going to get to the point where I played too well for my friends and wouldn't be fun to play against, so intentionally chose characters considered to be weak which were fun to play so that I'd not lose the people I played with. As my friends have gotten better and I've run into better people (JMoan and MSlano), its not as much of a concern but I've never really focused on a character since I started playing, so my mains remain terrible characters (I also play a fair bit of Bowser). I'm trying to play Jigglypuff more as I like her and do fairly decently with her, but not wonderfully, so am focusing on her more rather than just playing random characters as I tend to do.
My main problem is technical skill, or lack thereof - as I don't own the game, the main way I practice out new skills is by getting owned while practicing them "live". As such, a lot of my technical skills are far from perfect - I basically had to learn how to wavedash and shorthop while playing, as I have no other way to practice, so I'm still not perfect at them and other technical skills. Basically, I'm not quite experienced enough to be "good", but I've got pretty decent prediction skills and some strategy, though it is far from great. I have a very hard time beating MSlano and people of his skill range, so I'm an order of skill below him - I probably only beat him 5-10% of the time in singles, and generally if I do win its because he did something dumb like self-death. Oftentimes he'll two stock me, probably about 50% of the time. So, I'm not that good, but I'm learning.