A pitch isn't a summary, so you wouldn't give away the ending per se, but you would hint at it, since the resolution is the probably ultimate goal of your protag. You want to show the protag, problem, stakes, and conflict.
That bookends link JamieB posted is great for seeing good (and bad) pitches. She's done it a few times so check the archives. The best way to understand a good pitch is to read a them. The Miss Snark archives are also good for that. She did the Crap-O-Meter Hook contests in, like December-ish for a few years. Read a few hundred there and you'll be a master at it.