You know, I've always been curious about the fact that we weren't shown how K.O. and Professor Venomous ended up.
Because, you have to consider Venomous's actions and know how to balance them.
Canonically, Venomous has been stalking K.O. from the shadows, not as Venomous, but as Shadowy Figure.
And before anyone says that Venomous and Shadowy Figure are NOT the same person, let me clarify something.
In the episode "T.K.O.," Shadowy Figure tells K.O. that T.K.O. is just a collection of negative emotions he's been bottling up over the years.
This is further reinforced in the episode "Let's Go to Shadowy"(My mistake, it was actually the episode "Let's have a Stakeout")and the penultimate episode, where K.O. literally tells T.K.O.: "You are me, and I am you." With this clarified, we can say that ALL of Venomous's actions while transformed into his turbo version are UNJUSTIFIED.
His hunger for power and his insecurities explain them, but they don't justify them.
Furthermore, any mistake or bad action that Shadowy Figure commits, Professor Venomous has to take responsibility for it because, despite not being in his right mind, it harms him.
In the episode "K.O. vs. Fink," we see how Shadowy Figure manipulates K.O. from the shadows, giving him advice he shouldn't heed.
The same thing happens to T.K.O. at the end of the series, as he is merely used by Shadowy Venomous to gain power.
3-LITERALLY KILLING HIS FRIENDS IN FRONT OF HIM.
This definitely doesn't need explaining because we can all easily agree that Venomous messed up there.
We're not asking him to be gentle with K.O., BUT FOR GOD'S SAKE, he's your SON, and the first thing you do is kill his friends in front of him.
Even if he didn't know K.O. was his son, it's still incredibly HORRIFYING to traumatize a child to that degree.
4-The way they interacted.
This is more understandable than a mistake, since Venomous is a villain and OBVIOUSLY he was going to ask K.O. about things like enemies, etc.
But it definitely would have been much better if he had tried to interact more healthily with his child.
5-Not keeping his promises.
This can also be understood, since it wasn't shown how Venomous tried to get rid of Shadowy.
But just in case, I'll give it half a point.
This entire damn episode is what's wrong with Venomous/Shadow Figure.
And the ending, where he literally offers to leave for trying to express himself and open up emotionally.
I won't say anything more about this episode; it's everything that's wrong with Venomous.
7-The entire Shadowy Venomous and T.K.O. arc
If Carl is the most heartbreaking episode of the entire series, then I don't know what the T.K.O. and Shadowy Venomous arc is.
Those episodes are basically T.K.O. groveling for crumbs of Professor Venomous's affection.
I won't say anything about this arc either; I've had enough with Carl.
After analyzing all of this, we can agree that Venomous made a HUGE mistake with K.O. Manipulation, Harassment, False Promises, Deceit, Abandonment. K.O. HAS EVERY RIGHT TO GET RID OF VENOMOUS.
And anyone would tell you that those two should have ended things horribly, never speaking to each other again.
In the last episode, titled "Thank You for Watching This Show," for a few seconds, while the weddings of different characters are being shown, you can see Venomous and Boxman getting married.
In contrast, the other weddings were of people K.O. considered friends or even family.
And it would be downright OUTRAGEOUS of Venomous to invite K.O. to his wedding after all the trauma he caused him.
Not only do we see Venomous attacking the plaza in a pleasant manner, without any family drama between him and K.O. but we also see Venomous apologizing to Boxman for what happened with Shadowy Venomous, and from a few scenes, we can assume he did the same with Fink.
Combining all of this and following the threads that connect them, there's a possibility that Venomous apologized to K.O. and that they parted on decent terms—not necessarily good, but on terms where they weren't as angry anymore.
9- How did K.O. feel about it?
Possibly VERY hurt and angry, even to the point of hating him.
But before anyone tells me I'm taking the character out of context, let me remind you of the scene in "The K.O. Trap" where K.O. says he HATES Professor Venomous.
But considering the possibility that Venomous DID properly apologize to K.O., we can say that despite everything, K.O. was able to forgive him.
Obviously, he took his time to process things, clear his mind, and make a decision.
But one thing is clear: THEY APART ON GOOD TERMS.
(Or at least that's what I want to believe.)