Choice 1 After defeating the last boss, Sora, BHK, and Mickey give up their keyblades to restore the walls between the worlds and cause it to be immune to any kind of magic that will alter or break them, and life continues as if none of which occured existed, except, Riku having fallen in love with another woman (use your imagination for whoever she may be :fpcurious), Sora and Kairi walks toward the setting sun holding each other's hand.
Choice 2 After defeating the last boss, the heart of the boss flies of and creates a black vortex (or wutever the heck u want), which wraps around existence creates darknes. Then, you see a white light and hear, "Wake up you lazy bum!"
Choice 3 After you defeat the last boss, the four keyblade bearers sacrafice their pure hearts to protect the worlds' cores and hearts and create the walls between the worlds permanently impenetrable
Choice 4 Right before you get killed by the last boss, Kairi happens to make it and defeat it in one powerful blow with a keyblade of her own, and she continues on fighting evil with her 3 other companions (to the next game), for her keyblade is made from the remnants of the keyblades, which were destroyed when an evil source took over its power
Choice 5 You defeat the last boss, and continue on on the crossroads with BHK, Riku and Mickey, who team up to fight the next evil that dares to show its ugly mug
i had to do this cause it wouldnt fit in the option slots
i would just like to noe which kind
Edit: with the amount of comments dealing with S+K, ill add it in Choice 1