He's an incompetent bungler. 他能力不足，笨手笨脚。

She depicted her fellow investigators as bunglers. 她把和她一起做调研的这些人描绘成是笨拙的人。

See: bungle More examples

One generation hails you as a hero, but the next might denigrate you as a careless bungler.

As a boss, he's a bungler and mixer-upper.

She is intelligent but has no idea when she is being a bungler getting it wrong.

People think of him as an inept, irrational bungler.