Pawel Frossengellet from Felsic Current is quite a bad-ass yet seems to be the target of repeated undeserved physical assaults. From serious incidents (being shot in the head by sniper Fritri Waxkin) to minor ones (pratfalling when Fullian Fishk steals his sword, which Frossengellet was leaning on at the time).
Rincewind, in Terry Pratchett's Discworld novels. Other characters have pointed out how lucky he is to have survived everything he's been through (unknown to anyone, he's a favourite pawn of the Goddess of Luck). He, understandably, thinks it would have been luckier not to have been through it.
Also from the Discworld novels, the Bursar. Accidents are constantly happening to him; if someone throws away something, you can bet that it's going to hit the Bursar. He does not, however, mind (or even notice) since he is on a steady diet of strong hallucinogens.note He needs them to hallucinate that he is sane. It's complicated, and just a bit silly.
It spans in the fandom: at least one fanwriter mentions Dawlish only to have him defeated, usually in a humiliating way (once he even had him beaten by Dudley Dursley with a single punch, leading to Dudley declaring him a Squishy Wizard).
Ron Weasley tends toward this as well, especially in the earlier books in the series. Being the youngest boy in a large, money-strapped family, he's frequently saddled with hideous hand-me-down clothes, broken wands (the latter causing him to start barfing slugs during an attempt to defend Hermione), and other hilariously embarrassing misfortunes. The trope is subverted as the series becomes increasingly darker, with Ron's inferiority complex becoming a source of major despair and resentment, eventually leading to his Darkest Hour in book seven.
He also has a Self-Sacrifice Scheme in the first book, Nasty broken leg in the third, what ever the hell happens to him in Book 5...
Let's not even start on Neville who till the fifth book overshadowed Ron's victimisation and made it look tame in every possible way.
Agrajag, who is repeatedly reincarnated into the universe, and then always killed by Arthur Dent in some way. By accident.
Beginning with A Malady of Magicks and apparently never quite ending, the universe picks upon Wuntvor of the Western Kingdoms. It starts with his wizardly master becoming allergic to magic. Wuntvor doesn't get a moment's respite after that. Love, luck, demons, and the Monster's Union all wittingly or unwittingly make life difficult for Wunt.
By the end of the series, we've discovered that it's worse than that. Wuntvor is actually the current incarnation of the Eternal Apprentice. This means he has had and will always have this sort of luck, and he will never be truly competent at any profession, for all of eternity. On the other hand, he's maybe one of the greatest non-shonen embodiments of The Power of Friendship around.
The dwarf Bombur in The Hobbit. The poor fellow is constantly the first one on the menu by the enemies that capture them throughout the book, and often enough he's made to go last when put into pairs because of his weight. Not to mention he is the only one that falls into the Enchanted River...
Joe Buckley is included in almost every Baen book expressly so that he can be killed badly. In Mission of Honor there is the SLNS Joseph Buckley, latest in a line of ships named after a scientist who came to a spectacularly bad end, and almost all of which have themselves been destroyed or vanished. The one that actually appears in story fares no better.
Stephanie Plum can't go a single book without being this. If she's not having a car blown up or landing in a pile of garbage, she's getting dyed blue.
Also, Sita in the Ramayana. Exiled, kidnapped, accused of adultery and exiled again while pregnant with twins, the earth splits open for her when she pleads for an end to her miserable existence.
Trapped on Draconica: Ritchie does little else but get comical injuries. One time his fur fluffed up from Rana's lightening storm and another time he's covered in tar for no plot-based reason.
In A Song of Ice and Fire the people of the Riverlands get the worst end of the war, their realm is reduced to a war torn wasteland filled with corpses. Things get worst for them as they are now under the rule of the Lannister backed Freys.
In Warrior Cats, Percy in SkyClan's Destiny. Most of Stick's group gets away with just wallowing in Dodge's incredibly vague Offstage Villainy, but Percy is singled out for both having his eye ripped out and getting fixed. In fact, he doesn't have any role in the story other than having horrible things happen to him.