Well, you can decide for yourself if Ukyou is underhanded, mean and 
nasty or not from the list of when she's appeared in the manga, and
what she did of note...
I've only bothered to do up to the okonomiyaki sauce episode, from the
manga, because basically everyone agrees she's nasty after this.

In most if not all cases on your list,
1) she's perfectly justified in doing it (like, you list bashing Genma, the
Gambling King, or Tsubasa as if that was some great crime), or
2) it's not even that much.  (So she tries to act as a 'good wife'.  It may
prove that she's not a feminist, but it certainly doesn't show that she's
mean and deceitful.)

What about trying to kill unarmed, non martial artists? Or trying to kill
Hinako when she's a little girl? And she's justified in trying to kill a
girl who clames to be Ryouga's fiancee, for NO reason other than she's
Ryouga's 'fiancee'? And it's not that much that she sneakily tries to break
Ranma and Akane up by putting them through the anti-tunnel of love? And
bashing up Tsubasa is a crime - he didn't do anything wrong, unless you
count giving her gifts and saying he loves her deserves a bashing... Or
killing Akane, just because she and Ranma will get married, is 'justified'
and 'not even that much'?

Now, here's an exercise: go through the manga and list everything mean and
underhanded things that Ryouga does.  You can start with not telling Akane
that he's P-chan.

As I said before, that was EVERYTHING Ukyou did, not just the bad stuff.
So, if you want me to go through a list of all things that Ryouga did, I 
may if I can find the time and if I can be bothered. But we all know about
P-chan, and the only other things I can think of right now is trying to
use the disguse of being a little kid to get into the bath with Akane...
and when the oni made him do something bad ... but that's just off the top
of my head. He made up for it when he gave up Akane, without a fight, to
find her happiness with Ranma ... he wasn't selfish, unlike Ukyou and
Shampoo ... He put HIS happiness below Akane's. Ukyou and Shampoo didn't
give a damn about Ranma's happiness and tried to kill Akane, instead.

Kun-chan...