θα δεις τι θα σου κάνω εγώ → you'll be sorry, I'll show you, you're not going to get away with it, you'll pay for it

[Vasilis]

Αν τολμήσεις να το κάνεις, θα δεις τι θα πάθεις, θα δεις τι θα σου κάνω εγώ.

If you dare to do it, you'll get it in the neck, ...

[spiros]

I'll show you
you're not going to get away with it
you'll pay for it

[Vasilis]

Σε ευχαριστώ!

[aussieingreece]

(although this is not a direct translation, this is what I would say in this case ......)

(if you dare do it), you'll be sorry