Soul Full of Guns — John Birmingham

When monsters and dark magicks came back into the world it looked like Dave Hooper, aka 'Super Dave', might be our only hope. Thankfully not. Super Dave is dumpster fire of regret and disappointment for anyone who relies on him.
Colonel Ekaterina Varatchevsky of the Russian GRU doesn't want to rely on him. A deep cover agent operating in the US as Karen Warat, a successful New York art dealer, Karin is gifted with superpowers courtesy of killing a Threshrend Daemonum which attacks her gallery and eats rather a large number of Manhattan's 1%. Now she doesn't have to rely on Dave any more.
She has to target him.
This is her story. Not told by Dave. Because you can't trust that guy.