Did you spot the typo in the first line?
Single-handedly is a compound adverb and needs to be hyphenated, the same as you’d do with a compound adjective. (There is a rule against using hyphens with adverbs, but it applies to an adverb before another word.)
Add a comma after life.
Either end the second sentence with a period (the better choice) or use a real ellipsis (not that truncated thing).
Your trusted friend killed you and took the credit for single-handedly defeating the greatest evil and saving the world. As you lay dying, you hear a voice offering you a second chance at life, on one condition.
I feel as if there’s a word or two missing from the first sentence (the greatest evil what?), but I cannot think of anything specific to add.