Haven’t played Forces yet, and I never finished Colors, so I’ll focus on the other three. If we’re talking gameplay, Death Egg robot. Not necessarily because it was hard itself, but because (if I remember correctly) you fought it with no Rings. Egg Emperor is definitely the easiest of the bunch. Flight Level 2. That will be all. Egg Dragoon beat you up well enough, but I certainly beat it in all 3 versions easier than the Death Egg Robot. If you mean lore, Death Egg Robot is heavily outclassed. All it can do is stomp & jump. The Egg Emperor uses missiles, javeline attacks, and can unleash a shockwave, if memory serves, but aside from its thick armor, it’s not that great. The Dragoon is definitely the winner. In addition to its much wider range of attacks, it is only vulnerable in one or two locations. While Eggman did leave himself more exposed, that also allowed him to escape the craft when/if it failed.