Can anyone please get me the words of the phrase 'Scared of you?' in Cantonese?

geng lei ah? = 驚你呀?
another way to say is 怕你呀? (pa lei ah?)

驚 and 怕 have the same meaning.

Geng lei ahh = 惊你啊 = Am I afraid of you?
The above is good.
There is another one:
lv lei ahh (lju lei ahh) = 劣你啊= Am I afraid of you?
But this one is not so common as the first one. However, Hong Kong people will surely understand.

Geng lei ahh = 惊你啊 = Am I afraid of you?

It is ususally used when someone accepts a challenge from another person.