omg, I can't believe I forgot about "hakkiri"!! Thank you very much
It has been a few years since I've really practiced Japanese... I try to pull it out every once in a while, but as you can see, I'm starting to forget the obvious stuff T-T
EDIT: Is this maybe a little better? I tried to use elements of your sentence in mine.
R: Caster, hakkiri iwasete morau yo. omae mitai na yatsu to keiyaku wo kawashita koto wo kansha suru beki darou. moshi kyouchi ga chigattara omae ga kaikou shita mae ni sugu kakusu zo.
J: キャスタはっきり言わせてもらうよ. お前みたいなやつと契約を交わしたことを感謝するべき だろう。もし境地が違ったらお前が開口する前に すぐ隠すぞ。