Let's start with the basics: Stepan Bandera was born in 1909 in what is now western Ukraine. In 1959, the Soviet Union's KGB poisoned Bandera with cyanide and he died in Munich, West Germany.
Between those two dates, black and white quickly fades to gray.
In western Ukraine, many see him as a freedom fighter who battled domination by the Soviet Union and other European powers before and during World War II. They see themselves as the heirs to Bandera's struggle.
In eastern Ukraine, Bandera has entirely different connotations.