Well for a YuGiOh monster to be a threat didn't they need to be summoned by an Egyptian magi?
So, not really a threat if you keep the pressure.
As for Pokemon, the only serious threats are those giant Tentacruel, and captured Legendary Pokemon used for nefarious purpose.
Digimon on the other hand have the capacity of an adult human when matured or smarter, don't always need tamers to digivolve, and can destroy entire cities or potentially the world.
When I grew up I applauded Myotismon for actually taking over the town. He succeeded, and of course if it wasn't a kids show there would of been some on screen deaths. Aside from when Digimon die. Like that Wizardmon?...so many feels for Gatomon.