Wiktionary
betterer
a. 1 (context nonstandard English) (en-comparative of: better) 2 (context nonstandard English) better n. One who betters, makes something better.
Usage examples of "betterer".
Thou betterer of the Godfolk, enduring is thy fame: Yet as a painted image of a dream is thy dreaded name.
Well, then, supposing some dark night he should see Daisy on the street, just grab her, hold on tight and say: "Now, Daisy Rivers, I won't let you go till you promise you'll like me a great deal betterer than you do Dick Ray.
But," she says, the tears a-fillin in her eyes, "you knows much betterer than me, with your experienge, how little puts us out.
What dey had been doin' down dat hole was makin' der worl' a betterer place, Sergeant Detritus said.