Remember that Episode 140 of Kai corresponds to a later point in the original Dragon Ball Z (around Episode 235-237) because Kai removes the "filler" content to stay closer to the manga's pacing.
To watch , titled "A Hungry Monster! Buu's Incredible Power!", you can find it through several official and reputable streaming platforms depending on your region. Where to Watch
After being resurrected by Babidi, Majin Buu begins to showcase his terrifying and unpredictable power. The Z-Fighters, particularly Gohan and the Supreme Kai, realize the gravity of the threat as Buu easily overpowers them with his childlike yet brutal fighting style.
This episode highlights Buu’s unique biology—his ability to regenerate from almost any damage and his "innocent" but deadly nature. Quick Guide for Fans
Offers the Dragon Ball Kai (often listed as Dragon Ball Z Kai ) series as part of its anime library.
Since the merger, Crunchyroll is the primary home for the Dragon Ball franchise. You can find the "The Final Chapters" arc (which includes episode 140) there.
Most platforms offer both the English Dub (featuring the classic Funimation cast) and the Japanese Sub (original audio).
If you are binge-watching, Episode 140 leads directly into the high-stakes battles involving Vegeta’s sacrifice and the introduction of Fusion.