Translation:My cat is not friendly, it is even naughty.
The English sentence seems unnatural to me. You could say:
"My cat is unfriendly, even naughty".
"My cat is not friendly, but naughty".
You only use "even" to compare two things that are similar. But if you are comparing opposites (like "friendly" and "naughty"), you should use "but" instead. Even though "not friendly" and "unfriendly" mean the same, using "not friendly" makes the sentence sound unnatural.
Yes, I think we might just need here a more intuitive example of the word "bahkan" - this one doesn't translate very well ("My cat is unfriendly, even naughty" doesn't sound like anything anyone I know would ever say).