Then those scars fulfill their purpose, heh. Moreover, theres activating an actual confrontation. Don't worry bro, I'll pull a king mickey and intervene with my golden keyblade and revive you so it doesn't constitute as a loss XDDD.
Of course I kid. Given he's a guardian, as well as an obstacle, I'd say the only one thats got the best shot is Shiki, being realistic, leaving the graveyard to be revisited of course. While I can help, everything comes down the timing and when/if its too early its best to avoid the surmise of an event or situation. Like facing sephiroth at like level 45 and lasting sixty-seconds x_X
Edit; My advice for number one, would be to accept Cascade's guide. Yes an Ultimatum already, while that really is bad, it could be worse [you could fight the LS way too early]. Just remember, like in all KH games, you'll be retracing your steps at some point. Maybe not every single person, but alot of you will.