Not-So-Badass Longcoat

Goodnight, Lutessa Lena Luthor. You died as you lived: in a dumb Inspector Gadget coat.

—Chris Sims, Comics Alliance recap of the Smallville finale

Sometimes just wearing longcoat isn't quite enough to look badass. It can be because the longcoat in question is old, battered, two sizes bigger than needed or it can be because the character himself is lame or just acts as one.

Extremely associated with police detectives, FBI and inspectors. In fact association with the latter is so strong, you will have trouble finding a character named "inspector" without Not-So-Badass Longcoat of his own.

Examples of Not-So-Badass Longcoat include:

Anime

Subverted by Inspector Zenigata, from Lupin III; he can actually be pretty Badass at times, just not quite badass enough to take out Lupin and co.
Rotton the Wizard from Black Lagoon.

Film

Inspector Clouseau
Hiccup's coat/vest looks long enough to be a longcoat, but it more serves the purpose of making him look smaller than look badass.
Deckard from Blade Runner, despite having a lot of the typical traits of a classic Noir detective, is decidedly not badass, despite his longcoat. His sole two kills in the movie are women, both of which he shot in the back. The male replicants he pursues kick his ass up and down the field, and he's very narrowly saved from death both times(once by Rachel blasting Leon in the back, and the other time by Roy showing him mercy).
Harry in Home Alone wears a ratty overcoat that, rather than making him look badass (as he probably thinks it does), just makes him look trashy.

Literature

Dirk Gently in Dirk Gentlys Holistic Detective Agency typically wears a long, black leather overcoat (originally a part of his Suspiciously Specific Denial scheme of being labeled as a vampire), but spoils the effect with his funny hat and quirky behavior.

Live-action TV

Columbo
The Sixth Doctor's technicolor dreamcoat. It was a lot of things, but Badass wasn't on that list.

Theater

Collins' coat in Rent is pretty beat up, with the sleeve hanging off.

Video Games

Detective Dick Gumshoe from Ace Attorney series.
- Although he could Take a Level In Badass when required of him. He'd lose it as soon as he was done though.
Soviet Conscripts in Command & Conquer: Red Alert 3.

Western Animation

Inspector Gadget
Harvey Bullock of Batman: The Animated Series.