德行 literally means 'moral integrity and conduct', a formal noun for virtuous character. However, in spoken Chinese it is far more common in a sharp, ironic sense: describing someone's annoying or contemptible behavior, equivalent to 'the nerve of you!' or 'what a sight!'. This usage often appears in fixed expressions like 看你那德行 ('look at the state of you'). The tone can be derogatory or affectionately teasing depending on context.