Delta, Best ending is amazing. It's also amazingly difficult. The trick is to play for a few hours until you get the hang of it. If you don't save a Life Pot for it, you'll need even more surviving skill, or it'll be so much harder. Basically if you save it for the FINAL final boss, you have the Spur, and you have a decent amount of skill with Cave Story, you'll get it. The harder part is getting TO the last boss.