Finally got around to playing this again, and after a few tries took down Sandman (the only punch he gave me serious problems on was that delayed left hook, which was a problem because I grew accustomed to being ready to dodge left at any time to avoid all his other punches). Now that Title Defense is unlocked, I went ahead and defeated Glass Joe again (which was surprisingly hard due to having difficulties obtaining Star Punches, not to mention the opponents now seem to know how to dodge Star Punches). Looking at the mode, honestly I don't know if I'm going to bother finishing it. Sure, I'd like to unlock that 14th boxer (yes, I know who he is), but I'd much rather be boxing new enemies rather than all these old ones with new moves and fewer weaknesses. I also wish the rewards were completing the Challenges were actually worth unlocking, as they're glorified Sound Test Modes that I never bother with in any other game as well.