Word that describes someone that causes his own misfortune

I suggest hapless (from Merriam-Webster):

: having no luck : unfortunate

listed synonyms: unlucky, hard-luck, ill-fated, ill-starred, jinxed, luckless, snakebit (or snakebitten), star-crossed, unfortunate, unhappy

I think you mean

self-inflicted

(of an injury) having been inflicted on oneself by oneself

or self-induced

induced or brought on by oneself or itself

In addition to hapless, as suggested by Cornbread Ninja, I'd also suggest inept carries similar connotations (from the Random House Dictionary, via Dictionary.com):-

1. without skill or aptitude for a particular task or assignment; maladroit: He is inept at mechanical tasks. She is inept at dealing with people.
2. generally awkward or clumsy; haplessly incompetent.
3. inappropriate; unsuitable; out of place.
4. absurd or foolish: an inept remark.

Inept carries with it the idea that one has voluntarily exposed oneself to the sort of situation where these things apply.

I do not know a single word to describe such a person, but here are many common idioms in English to refer the act of suffering from one's own action.

• hoist with one's own petard
• fry in one's fat
• be one's own enemy
• stew in one's own juices
• be rightly served

Someone who subconsciously undermines his own success is inflicting self-sabotage. Someone who sabotages is a sabotager or saboteur, and we can combine "self" into a word by replacing it with the "auto-" prefix, hence: autosabotager, or autosaboteur.

Of course, this is a rather narrow nuance. This question seems to have a broader interpretation.

For instance, someone who suffers setbacks due to making foolish mistakes isn't inflicting sabotage; that psychological element is lacking.

Words used for someone who brings avoidable calamity on himself by his own foolishness, and not through any bad luck, are simply general words that denote any sort of fool: buffoon, incompetent, imbecile, and so on. In all the myriad words that describe a fool, there is an understood element, almost by definition, that this is a person who causes bad things to happen to him or herself and others due to poor planning and reasoning.

What about someone who doesn't lack intelligence, but suffers setbacks due to exercising poor risk management? When a calamity occurs due to bad luck, luck cannot always be blamed; sometimes bad luck calamities could clearly be avoided by reasonable steps to manage risk. People usually do not intend for traffic accidents to occur, yet these are caused by mistakes and unnecessary risk taking, and blame is assigned accordingly, not simply on bad luck. Those who take unnecessary risks can be described with adjectives such as careless, irresponsible, nonchalant or blasé (with regard to risk). "His nonchalant attitude always lands him in a bind."

Depending on the severity/seriousness of the outcome I guess you could also use the following terms:

Frankenstein

Franskenstinian

• a monstrous creation; especially : a work or agency that ruins its originator.

• a thing that becomes terrifying or destructive to its maker.

• a person who creates something that brings about his ruin

The corresponding idiom is Frankenstein's monster

Giving extra powers to the army turned it into a Frankenstein's monster that is now threatening to overthrow the ruling party.

King Midas might be appropriate.

There's also the "Midas touch" which is generally considered a good thing (everything you touch turns to gold) but the original story is a tragedy (he turns his daughters to gold) which he brings upon himself via greed.

Or if he just trashes everything, there's King Midas in reverse.

In The Netherlands there is a writer, poet and performer known as Johnny the Selfkicker. Paraphrasing Wikipedia, the Selfkicker "has proven to be worthy of his name because of wild, often haphazard performances, during which he never fails to work himself into a frenzy, which often results in him collapsing right in front of an astonished audience." Download a picture of the Selfkicker at http://sdrv.ms/18EwcKs . Johnny even looks the part of the selfdestructor. I'm sure the Selfkicker would love to have his name officially adopted by the English language.

PS When and how does a new member acquire the right and ability to attach a picture?

self-destructive. "Shooting one self in the foot" and "Digging one self into a hole" are my favorite not-one word options.

nemesis means

A person or character who specifically brings about the downfall of another person or character

so, self-nemetic is the person who is the cause of his/her own downfall.

I might use a well worded phrase in place of a single word. You could state that he was the 'harbinger of his own misfortune' and it would suffice.

harbinger — n 1. a person or thing that announces or indicates the approach of something; forerunner

How about shlamazel, a shmoe, a shemendrick. A shlamazel is one who has cronic "bad luck". A shmoe is a foolish person. A shemendrick is A man who messes things up, always loses and feels miserable. An unfortunate asshole. Closely related to Schlemazel and Schlemiell.

Fool

a person lacking in judgment or prudence - Merriam Webster

stupid defines someone lacking the ability to make good judgments, while fools have the ability but do not use it, when they do something foolish.

The lack of judgement does not necessarily cause one's misfortune, but the risk is so high, that anyone knowing the risk, is in fact responsible for causing their own misfortune when it occurs. So, looking into the past, someone who causes their own misfortune from lack of judgment or prudence was a fool...having done a foolish thing.