Pit gets all his damage off of grab setups. Your main plan should be to get your opponent offstage, then use your extended reach to gimp. Recommend seeing Nairo for this. If you vs someone campy, don't always use guardian orbiters.  Usually, you want to go on platforms, or make mind games with arrows. Pits best move is defiantly dash attack (IMO). Its quick, and can be used as a stuffer. Overall, Pit can do good against heavies, cause of juggling and the capability of arrow control. He does bad against fasts, like Pikachu an sheik. They can use quick attacks to stump you out. What you can do is be offensive. use mostly ariels, and look for oppenings. :)

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