I wish I had more vids of S!C, the best german wario... He does crazy **** with bike tires which not only make approaching a very difficult task, but more often than not will lead to 40%+ punishes, and death anywhere starting around 50%.
If you can, try to keep the wario away from his bike. It's one of his most important tools in the matchup (especially when broken!), between tires, bike recovery, and flat out running your *** over and looking cool while doing it. If you can get wario offstage, and his bike isn't near him, he has two options: UpB, and Fart. If he farts, he has to wait quite a while before using his best kill move again, and often he just doesn't have the fart to use. If he upBs, he's easily edgehogged and/or gimped. Good warios do not lose their bikes often, but if you see an opportunity to keep him away from it, DO IT. And steal his tires. I am scared ****less of tires since playing against S!C. I should probably ask him for input on this...
Don't stale your kill moves. Seriously, Wario lives FOREVER and kills you retardedly early; you don't want to make this worse by ensuring that your dsmash is so stale that it makes last year's halloween candy look attractive. You really shouldn't let it come to this point, but it can and probably will occasionally happen that you barely kill him at 200% with an Nair or something, and then he comes back and ***** you at 50 with a half waft. I'm with Kaffei on this one-run the **** away from it. Fully charged, it does a lot of damage, but it won't kill you until like 80+, later with good DI. BTW, careful blocking a full waft if your shield isn't fresh, that thing does 42 damage with good shieldstun and can easily break shields.
Counterpicks... I honestly really like FD in this matchup, but there's probably better. If norfair is legal, ban the **** out of it; wario will MURDER YOU on Norfair, just like he'll murder pretty much every character in the game (that stage is SO ****ING STUPID FOR WARIO). Otherwise... I dunno, I kinda feel like Brinstar isn't that great for us in this matchup. We want the static terrain to wall him better... FD, SV, YI? Don't like battlefield for similar reasons as Brinstar. Frigate and Delfino are probably good choices as well.
EDIT: In case anyone wants a ratio, I honestly think this matchup is 60-40, maybe better, in our favor. Wario is powerful stuff, but we can wall him out fairly effectively. Like, really effectively. Good spacing, and he simply will not get in well.