Compare this to Gemini who has allegedly killed a handful of his henchmen off-screen for the littlest reasons! That man is truly evil (but he's also very incompetent).

DNAmy who basically toys around with human lives for her own twisted obsession over Cuddlebuddies. She doesn't really care whether or not others are harmed as long as the results are there.

Dr. Drakken would definitely have been able to take over the world a long time ago if his ego wasn't in the way. He has some seriously dangerous inventions/outsourced projects... I mean he tried to erase all the oxygen from the world, TWICE. His problem isn't "I have too much goodness in me" it is "I have too much pride that I cannot cast aside". THE ONLY REASON THE SUPREME ONE FAILED IN KILLING OFF KIM WAS BECAUSE BUFFKKEN EGGED HER ON TO GLOAT AND RUB IT IN HER FACE > thus revealing the separation of team possible and unlocking Ron's ultra-instinct powers.

Ron is 'evil' but not necessarily 'evil'.

He's evil in the sense of 'This is what it takes to be a villain' but as a person himself, he's well, short-lived.

Towards the end of the episode 'Badboy' he proclaims:

"The inhalator has been set to go off in five minutes. When it does quakes are going to shake the world to pieces."

and then he later adds:

"--I’m just getting warmed up. The inhalator was to keep you busy while I worked on my real evil plan. My mega-weather-generator. All will fear me and tremble beneath my storms, and then hand over to me the world’s supply of Nacos. Booyea!"

He has the potential to do really bad things but he isn't evil in the sense of what the villains try to obtain: absolute power and world domination. Ron's wants in the episode 'Badboy' are just amplified:

- Getting revenge on Cousin Larry by bringing him humiliation (but not death).

- Getting the world's supply of Nacos.

If he went through with the last one, he'd be easily defeated because he'd eat himself into a fast food coma, he would get his stomach pumped at the hospital and Kim would switch his evilness with Drakken, dividing it again. Drakken would try and intimidate Kim and Ron but Kim will point out that she isn't sure if Drakken could handle combat with her since Shego's back at the lair (she would not go along to the hospital). Drakken would get nervous, not wanting to get beaten up and take his leave.

The reason Ron goes after/fights Kim is because she's in the way of his plans. Not necessarily because she is his archnemesis, 'cause she's not. But he knows how capable Kim is in stopping everyone and the man really wants his Nacos.

TL;DR: Evil Ron is evil but not necessarily dangerous world ending evil because that's not what he really wants. He literally took all of Drakken's 'Playground bully' evilness.

Anyway, this is my take on it, hope it makes sense.