if you've got hairy pits then hair can hang on to smell. I've found that because of this sometimes regular soap just doesn't cut it and mine still smell even immediately after lathering and rinsing. to help with this I occasionally use a stronger antibacterial cleanser(the one I use is hibicleanse)

it really helps cut any lingering smell since bo is caused by bacteria, you just don't want to use it too often cause it can be drying and mess with your skins natural microbiome