Another word for really
actually, in reality, indeed, genuinely, certainly, surely, absolutely, in effect, positively, veritably, authentically, as a matter of fact, in point of fact, in actuality, upon my honor, legitimately, precisely, literally, indubitably, unmistakably, undoubtedly, categorically, I assure you, I'll answer for it, be assured, believe me, of course, honestly, truly, admittedly, nothing else but, beyond a doubt, unquestionably, as sure as you're alive*, no buts about it*, without the shadow of a doubt*, you said it*, you bet*.
To a remarkable degree
indeed? honestly? for a fact? yes? is that so? what? are you sure? no fooling? no kidding?* cross your heart and hope to die?* on your honor?* you don't say?* the deuce you say!* blow me down!* ain't it the truth?* you said it!* do tell?*