Allah tabaraka wa ta^ala said:

(إِنَّ الْحَسَنَاتِ يُذْهِبْنَ السَّـيِّئَاتِ ذَلِكَ ذِكْرَى لِلذَّاكِرِينَ )

Verse 114 of Surat Hud means that the good deeds erase the bad deeds.

The Messenger of Allah sallallahu ^alayhi wa sallam mentioned in many sahih hadiths the interpretation of this verse, among that is what was related by Muslim in the sahih that the Prophet of Allah sallallahu ^alayhi wa sallam said what means:

“Would anyone of you be powerless to gain one-thousand good deeds a day? He can do that by making tasbih (to say “subhan-Allah”) one hundred times, by doing that, he will have one-thousand good deeds recorded for him and one thousand bad deeds erased for him.”

This hadith clarifies that the one single good deed erases ten of the bad deeds, this is the least thing that the single good deed does; also the one single good deed could erase more than that of the bad deeds. The proof is that the Prophet sallallahu ^alayhi wa sallam mentioned that making tasbih (to say “subhan-Allah”) one hundred time earns the person who says it one-thousand good deeds, moreover, he said that the one who says “subhan-Allah” one-hundred times would have one thousand bad deeds erased for him; it means one-thousand sins.

The Messenger of Allah sallallahu ^alayhi wa sallam did not limit that to the small sins, so we say that it is possible that Allah would make one single good deed erase some of the enormous sins.