He did have influence as a literary critic. In a word in Bologna “crystallization” has not yet begun. 
In his works Stendhal "plagiarized" reprised appropriated excerpts from Giuseppe Carpani Théophile Frédéric Winckler Sismondi and others.
Known for his acute analysis of his characters' psychology he is considered one of the earliest and foremost practitioners of realism as is evident in the novels Le Rouge et le Noir (The Red and the Black 1830) and La Chartreuse de Parme (The Charterhouse of Parma 1839). .