What German artist is famous for her etchings of the working class?
There are actually many people named Peter Alexander who are famous for many different things. One is an Australian fashion designer, branding his own sleepwear and underwear. Another is a famous German film actor who died in 2011. There's a famous Peter Alexander working in the White house as a journalist, and lastly we have the 74 year old "light and space artist", again from America, this one specializes in LAX art and Sculptures.
That cannot possibly be answered as there are many highly influential and brilliant artists working in each style. And there are many, many styles. Art is also continually evolving and building on itself, and each artist must find his own niche and expression, so no artist can be singled out as the most influential on art history.