That Combo-Breaker medal was pretty ridiculous to achieve especially considering it was almost entirely luck, but it also holds you back from that elusive Determination medal.
As for Determination medal, here is something you will need to know. Yes, first get all other medals. However that's not enough. After you get all other medals, start a new game (and it will award in-game only at this point) however this is still not enough. Keep playing a few more games then about 5 or 10 minutes later check if you have the medal and *now* you probably have it.
Also, not really a fan of the whole intentionally score badly to get all possible endings game mechanic. A supremely superior game mechanic is the high score unlocks all lower score requirements as well. It's not really fun (or fair) to make people who are good at games have to intentionally pull games to meet some arbitrary low score requirements.
I understand you might think of this as "rewarding effort" but it's really less rewarding effort and more punishing skill. It's not fair to the better players and worse players will naturally do this anyway.