Filch is the caretaker at Hogwarts. He has a deep dislike of all the students of Hogwarts and was glad to get to finally punish their misbehavior "properly".
At the end of the war he was tried but wasn't sent to Azkaban; as he was a squib surrounded by Death Eaters, causing reasonable doubt for coersion. But he was never allowed to work around children or teenagers again. So he went out into the muggle world and got a job at Tesco as a maintenance man. He worked his way up to Departmental Assistant Manager before he died of old age.