a tard and a half - a human garbage can who doesn't know what they're doing and

a human garbage can who doesn't know what they're doing and makes your life harder just by existing

My brother is a tard and a half. He tried to mow the lawn and ended up cutting the fence.

My coworker is a tard and a half. She spilled coffee on my laptop and then blamed the cat.

My dog is a tard and a half. He chewed up my homework and then sat on it like it was a throne.