Worthy doesn’t simply mean kind. For example, Spider-Man is pure-hearted, but he isn’t fully confident in his own abilities (at least for a while). This is why the Flash couldn’t wield Mjolnir.

I’m going to define worthiness as selflessness, bravery, and honor.

In that manner, the best option is pretty easy.

Wonder Woman has lifted and wielded the hammer in a crossover between Marvel and DC. She is a warrior with a great moral compass, yet she will do what is necessary. That’s where the Flash fails. (Cyborg could technically lift it but he wouldn’t be able to use it as only living beings can lift it. As you can see in the MCU, Vision can lift it but not use the hammer’s powers.

Technically, Superman also wielded the hammer, but Odin let him.

Honorable mentions: Aquaman, Kyle Rayner (Green/White Lantern), Hal Jordan (Green Lantern), John Stewart (Green Lantern), Superman, Shazam, and Nightwing.