I think it was 999 HP to execute which isn't a lot after about Level 30ish. It can take out up to THREE defenders and has Invisible Shot properties. If you don't know what that means because you haven't gotton far enough in Blitzball, then you probably shouldn't even worry about Jecht Shot 2 (or Invisible Shot for that matter) because all it does is give you the chance to bypass the goalie's CAT stat. During the early stages of Blitzball, the goalie is easy so it's not required. But the more you play, the more the goalie tanks up (blardy Nimrook). Eventually it gets to the point where Invisible Shot HAS to be used.

EDIT: And Jecht Shot 2 is Tidus' uber key technique, so you'll need to learn the other three key techniques (which are listed in his player info menu). They're pretty easy ones to learn, I don't remember exactly what they are but it's just stuff like Venom Tackle etc. Trust me, it won't take long. I'm not sure if Jecht Shot 1 is a prerequisite for the move either but I'm pretty sure you have it anyway.