Katarina's a really good choice.
Why? First off, she doesn't have any
skill shots. That means a script wouldn't have to worry about lining up any tricky shots, it could just go all in.
Second, her
abilities reset every time she gets a kill or assist. So if the script is controlling her, it could take advantage of this and just chain together a bunch of kills one after the other.
Third,
Katarina's really good at roaming and getting kills in other lanes. In which case the script could look at stuff like how much health the enemy has, where they are, and whether their abilities are on cooldown to decide the perfect time to strike.
Her
Shunpo (E) gives her a ton of mobility because she can teleport to other units. This means a script could use this to make some sick plays, escape from a fight, or dodge enemy abilities.
(I did some research into this.
)