Delta Leland Kitchen Faucet Removal
That thing is so hopelessly corroded that the only hope I see is to use one of the following:



(Picture Source: https://www.dremeleurope.com/general/en/cut-offwheel32mm-184-ocs-p/)



(Picture Source: https://www.amazon.com/Stanley-Hand-Tools-20-807-Mini-HackTM/dp/B00009OYGD)

Any type of hammering, prying, twisting or chiseling you try to do is liable to either bend/break your sink or damage the finish if it is a porcelain type sink.