what genre was Lord Byron most known for?

His genre was in poetry, true, but mainly romanticism.

He wrote prolificly, some of his works are satirical, and

his magnum opus, Don Juan, a poem spanning 17 cantos, ranks as one of the most important long poems published in England since Milton's Paradise Lost. At the time of his death he was a celebrated poet; it is shocking to know that his friend and publisher was shocked to know how loved he was by the common man ;-)

Poetry. http://englishhistory.net/byron.html

He was known mainly as a poet. He wrote The Giaour, which was a poem.