Flattery used for manipulation.
It’s not just flattery: aka being kind and sweet and excessively loving to an individual, because you like them. And it’s not just being romantic.
People can try to use flattery or big gifts and have it not be received well, but that’s not the same as love-bombing.
Love-bombing is when excessive flattery/kind gestures are used as a tool to make a negative thing seem ‘justified’ or ‘not that big a deal’.