How to open client?

So I can't even open the client anymore. This issue has happened multiple times and every time I had to uninstall and reinstall league just to be able to open the client so I can play. At this point its not worth waiting for league to reinstall anymore cause the client is malfunctioning. I play on mac and it says that the client is "incomplete or damaged" like that wasn't the case when it worked the day before. Just wondering if theres any solution or am I completely unable to play league anymore.