Double-edged blades are illegal to carry here in California. There are less issues to deal with using a single-edged blade.
If you think slashing is only for "hurting" people, you don't know what you're talking about. An entire karambit style of fighting wasn't created just to hurt. A good cut to the neck, wrists, arms, or face are powerful deterrents. If you're that hellbent on killing the guy (though at that point in time, you could probably run), then follow up viciously. I doubt the assailant will enjoy it.