The exclusion of "that".

Sentence: "I'll tell you, if I ever had the chance to get my hands on him, I'd be extremely violent."

Would a colon be appropriate after "I'll tell you", or is a colon correct? A comma does not seem appropriate given it's an independent clause preceding it, or is this introductory information?

I'm leaving out "that" for dialogue purposes so it could have read "I'll tell you that if i ever...".

Any suggestions/thoughts? Thank you again