In the bittersweet finale, Paul returns to his village as a normal boy, greeted by friends old and new. The last scene shows a small rainbow forming over his workshop, hinting that miracles still exist in small ways.
It seems you're referring to (ポールのミラクル大作戦), also known as Paul's Miracle Operation — though this title is not a widely known mainstream anime series. It’s possible you’re mixing together a few different shows, or referring to a very obscure or misremembered title. Paul no Miracle Daisakusen Episode 50
As the team struggles to purify the Core, Paul realizes that true miracles don’t come from machines, but from people believing in each other. He sacrifices his Miracle Gear (his powered suit) to reboot the Core, losing his ability to ever use a miracle again — but saving the world. In the bittersweet finale, Paul returns to his
“Thank you for believing in miracles — and in Paul.” It’s possible you’re mixing together a few different
In the meantime, if you intended a in the style of a classic 80s/90s comedy-mecha or adventure anime, here is a creative sample: Title: Paul no Miracle Daisakusen – Episode 50: “The Final Miracle – Beyond the Rainbow”