YOU SAID:
I made him an offer he can't refuse
INTO JAPANESE
私は彼に断れない申し出をしました
BACK INTO ENGLISH
I made an offer that I couldn't refuse to him
INTO JAPANESE
私は彼に断ることができない申し出をしました
BACK INTO ENGLISH
I made an offer that I couldn't refuse to him
That didn't even make that much sense in English.