「、、」「！」
"To tell the truth, I'm afraid of heights." "Coward!"
Literal
"Truth [object-を] say-[if-と], me, height-fear-disease [explanatory-なんだ]" "Coward [emphatic-っ]!"
実を言うと ('to tell the truth') is a standard sentence-opener for confessing something. 俺 is the rough/masculine first-person pronoun. 高所恐怖症 is a heavy compound — 'high-place fear sickness' = acrophobia. The ~症 suffix means 'syndrome/disease.' 臆病者っ has the small っ at the end representing a sharp, clipped pronunciation — a cut-off glottal stop common in exclamations.