A.T. Robertson Commentary Mark 14:31

"But he spake exceedingly vehemently, If I must die with thee, I will not deny thee. And in like manner also said they all." — Mark 14:31 (ASV)

Exceeding vehemently (εκπερισσως). This strong compounded adverb only in Mark and probably preserves Peter's own statement of the remark. About the boast of Peter see on Mt 26:35.