OLIMAR:
approach diagonally
dont bother hitting his sheild if you dont have
double jump (using bair out of parachute so u get ur jump back is a decent mix-up, dont let him expect it often though)
Dtilt kills pikmin, is fast enough that its decent to kill thrown pikmin without him getting into your zone
SH Nair helps get closer to him without taking too much damage
Dont get grabbed if there is a white on you, try to kill it ASAP
Dthrow to Dtilt next to the edge is a good set up for a really easy gimp if you can read his reaction.
Bait his whistle as he falls. If you fastfall Nair as a reaction to his whistle, you should get him with the end of Nair to hit him back up. Uair also works, and in fact is a real legit kill because the first hit wont hit him away and the 2nd hit with the killer knockback will catch him, so he sets up his own death; oli dies pretty early upwards.
Usmash has pretty big range, but if you are between Oli and the pikmin vertically you can poke him quite safely, especially if you still have your double jump.
Oli can run up and grab or usmash very fast, landing Fair on the ground or Dair is quite bad. In the air or rising its ok but to actually land these is more dangerous against Oli then it normally is. Be that little bit more careful.
Supposedly Oli likes Lylat, pretty sure he gets more purples, which are the big hassle for GaW. I suggest killing them with a strong move if you can, helps us to approach and removes the big scare, Uthrow with a purple. But anyway, I think Lylat benefits us more so I wouldnt fear it. Oli likes to get under platforms which makes it hard to approach diagonally or use the aerials as early as we would like, but bair reaches under Lylat platforms well and spaces to the tip quite nicely.
Oli can be juggled easier than people think, requires more reading than usual tho
If he looks like he's only JUST going to make to the edge maybe, you arent sure, fast fall Nair to pull him down and UpB to spike him. People think edgeguarding is the godsend vs a tether recovery. It is really good, but you shouldn't let it stop you from going for a legit gimp, in fact the mentality people get from this helps Oli to get gimped less, lol!
Uair and other things that can string can cause hassles, UpB away is ok if u have your jump. Oli can actually juggle GaW without a jump, its pretty serious.
STAGES:
Battlefield is good for Olimar, personally I hate it at least.
Delfino is a decent CP for us. I know Oli is ok here, but for GaW specifically its not a good choice for him.
Frigate is also good, but beware of more purples and prepare to camp hard during that transformation that has two ledges, because its hard to approach him if he's in the middle.
That brings me to my last point: Olimar is a character with powerful stage control. If you can keep him out of the middle of the stage or away from under a platform, he should be feeling quite vulnerable (and he is too). You can abuse this better with practice. Approaching him when he is on the ground is the hardest part of this MU, our approach is really the only place where we lose out. Our platform abuse and air game is better than his. Don't fear the MU, so overcomeable.
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At the major I want to, there was an Olimar player who is much better than me as a player in quite a few ways. He kept amazing calm, made patient and very thought through decisions and made very good reads for the kills that i suspect he also used purposeful conditioning to get, or he just analysed people very hard lol.
He came 2nd, but I beat him in a MM. I know the Oli MU very well and was able to abuse a few things, although I was rusty on it. He learnt the GaW MU enough to have a chance against me in the bracket, and I kinda threw the first game <___< which was of course dumb, because even though I 2-stocked him on the CP he managed a clutch victory on his CP even when i was trying hard.
Anyway just from playing those games I've remembered this, if I went back to that bracket set recalling all this I probably would have gotten away with throwing the first game.
I don't know if my experience willl help you beat Fino though, JOEY... Fino is real goods.
Hopefully Smiley can start winning though
Good luck to both of you
ps. yes this post is mildly colour coded.