From Longman Dictionary of Contemporary Englishbest of allbest of allBESTused to introduce the fact about a situation that is even better than the other good thingsIt’s clean and well-located, but best of all, it’s affordable. →best
Examples from the Corpus
best of all• Of all the participants Reagan came out best of all.• I appeal to all who have ever known this best of allhospitals - fight for Bart's.• But Black Mountain was often not the best of allpossible worlds.• That was the thing he lovedbest of all: running free.• The Corps was a know-how, can-dooutfit, possibly the best of all the outfits that came to town.• I'd have liked best of all to have stuffed his mouth with hay.• Oh, but best of all was the chair in which I myself was destined momentarily to sit.• You can lose five pounds a week on this diet. And best of all, you never have to feel hungry.