First Knight - Capes & Masks, #1

Eighteen-year-old Alex Fry (Beams) thinks he's seen it all in his year and a half as a part-time sidekick. That's why he's surprised when the police call him and his boss to investigate the gruesome slaughter of a local crime gang. Nineteen of Golden City's most wanted killed in one night by one man. The culprit: A supervillain knight known as Slasher seeking to conquer Golden City in the name of his mysterious king.
Slasher is willing to kill anyone who stands inthe way of his conquest of the city and Beams and Rubberman are at the top of his hit list. Now Beams must use all of his cunning, strength, and powers to defeat Slasher and save Golden City. Yet when Beams' own failing powers threaten to kill him, defeating Slasher may be the least of his troubles.