Vengence is one of those very mallable words.
To me, it means exacting pleasure from carrying out an act intended to harm in retaliation to a perceived event.
So when King David was asked by God to take a Census and took the Census, God killed 40000 Jews as vengence for David obaying him. (its fruity, but it's scripture OK?)

Now you will not find a Christian or Jew who will say that this was God being vengeful these days. They explain such actions as God enacting rightful justice as is his ..err...umm..god, err given right...Hmmm...(just confused myself there).
His Justice is perfect and merciful, and if we cant understand him slaughtering a mid sized towns population for obaying his orders, then we are not in the full picture. God works myseteriously and it is not for us to doubt or try and reason it with our puny human minds.

Personally, i think David took a Census, and then the sewage system failed and Dysentry wiped out a bunch of people. Dave stuck two and two together and made 23,435. It got written in, and bading!