Hello.
OK, my last words, my last seeing, and talking to you, bye. I never wanna harm you.
Are these words grammatically fine and natural?
Bye.
No. Try writing it again starting with "This is the last time I will..." and see how it sounds then.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
...and wanna is never grammatical.
One's "last words" are what they say before they die.