English word for someone who often and unwarrantedly imposes on others

"self-serving" comes to mind.

• "serving one's own interests often in disregard of the truth or the interests of others". MW

• "serving one's own selfish interests, esp. at the expense of others." Collins

• "habitually seeking one's own advantage, esp at the expense of others." TFD

e.g. a self-serving character, self-serving behavior, a self-serving trait.

• selfish
• inconsiderate
• entitled

All come to mind.

In English someone who does the things you describe above, would be said to be taking advantage of someone/something/a situation etc.

take advantage of sb/sth B2 disapproving Cambridge English Dictionary

to treat someone badly in order to get something good from them:

Examples

I think she takes advantage of his good nature.

I know she's offered to babysit, but I don't want her to think we're taking advantage of her.

In English, I think annoying (a word with more force than "inconvenient") is nice. I do not agree with the precise answers given before. There is an endless odyssey to be someone who often unwarrantedly imposes on others... Annoying fits perfectly.

If we assume, v.g., your question is limited someone who take advantage, it is the same as

"The type of human specimen if I could choose 'between next to Strontium-58' and 'next to such kind of person', I'd stick with Strontium-58" -- when it can be "Strontium-58" and/or "Caesium-137", "Plutonium-237", "Uranium-235", mutatis mutandis, of course.

I like the uncommon but very good second definition of Flatulent:

2. pompously or portentously overblown

which also hints at Pompous and Overblown. I think you would need to say "A flatulent personality" to make it clear they don't just have intestinal problems...

You may need a noun and an adjective to include all the connotations.

The attitude described makes me think of "cheeky", or in formal language, shameless and insolent.

I also came across brazen (WhordHippo)

bold and without shame.

You must not despise "parasite", it is not only connected with money, it means

One who habitually relies on or exploits others and gives nothing in return.

or

a person who receives support, advantage, or the like, from another or others without giving any useful or proper return, as one who lives on the hospitality of others.

You might call such a person a self-centered / spoiled brat, but "brat" is colloquial.

The whole context makes me think of the expression to act like a princess used about a woman who expects everyone around to bow down and serve them. Urban Dictionary says that the expression "to act like a prince" can be used with a similarly negative connotation.

Check the explanation of the Princess Syndrome in the Urban dictionary (it might help you find other expressions with the meaning you are looking for.

A little stronger and more informal than just calling them "entitled," you could say that they're "acting like a spoiled child" (possibly "spoilt" in the UK).

Where "spoiled"/"spoilt" here means:

Injured in character by excessive indulgence, lenience, or deference

So you're commenting on the fact that they're acting as if they expect and are deserving of your indulgence, lenience and deference, and doing so is childish and detrimental to their character in your eyes.

If you're looking for an informal option, you might use mooch or moocher here:

a person who is supported by or seeks support from another without making an adequate return

—Merriam-Webster

Note that this seems to have different meanings in the UK, but at least in American English, this would be understood to refer to someone who (for example) constantly asks for things from their friends, but does little in return.

Here a few on the slang-ish side: freeloader, scrounger, sponger, deadbeat/ dead beat.

I would like to add the word groak as a humorous option. It is well explained in this answer.

The person would be a groaker, or possibly a groak. It is typically applied to a person or animal hanging around in the hope of being offered food or drink.

If you're looking to be particularly venomous, you could consider parasitic. It's the adjective form of parasite, an organism that lives on or alongside a host organism to the detriment of the host.

Informal examples typically consist of comparing the target of criticism with an animal that is parasitic. You could outright call them a parasite but thats a bit arrogant imo.

Some typical examples consist of; "Leech", "Mooch", (or if youre feeling especially cultured and saucy) "Filthy Imperial Milk Drinker".

But mostly the first two.

I would call this person a leech

leech(n): a hanger-on who seeks advantage or gain.

Literally, a leech is a blood-sucking worm that attaches itself to any creature it can and is difficult and painful to remove. This is a perfect analogy for this type of person.

Most relationships are based on reciprocal altruism. If you do me a favor, I owe you one. But leeches are worse than useless, because they’re anyways hanging around, taking advantage of your generosity without ever giving anything back.

burdensome

They're a burden on others (or at least an imposition).

Compare with these words:

• troublesome
• bothersome
• worrisome

Colloquially, these words are often used to express exasperation (or mere annoyance, if said jokingly) when someone creates a problem. But burdensome is more serious; it implies that someone (or their behavior, rather) is a problem. That is, it suggests not carrying one's own weight or regularly taking the lion's share (thus, being a burden on others, whether it's intentional or not).

BTW, instead of "takes a lot of room," we'd be more likely to say that they're a lot of work (alotta-lotta-lotta work).

(US, SE Region)

"Manspread, manspreading, manspreader" is slang frequently used to describe someone taking more space than warranted on the subway in NYC (and elsewhere apparently), by having their legs spread so far as to prevent someone from sitting next to them on the bench. There's also a wikipedia article.

I'll add "high maintenance" to the list. This refers mostly to someone who is emotionally needy. They have some minor problem and everyone has to drop what they're doing and sympathize for way too long. They're the one who can't decide the exact perfect thing to order for lunch and everyone else has to extend their lunch hour. At a conference, they find a motel 1 dollar per day cheaper, but 5 miles farther away, and then insist that someone else, who rented a car and paid for the more expensive motel, come and get them each morning and return them each evening.

It's just exhausting being their acquaintance. "Are you upset? You seem upset. Did I do something? Are you mad at me?" No matter what emotion you exude, it must be about THEM.

A few more "decorative" words that might fit the bill.

1.) Gluttonous

using more than you need:

2.) Grasping

(of people) always trying to get and keep more of something, especially money:

3.) rapaciousness

the quality of having or showing a strong wish to take things for yourself, usually using unfair methods or force:

A hog; A bogart

Someone who takes more, or for asks more, than their share of physical things is informally called a 'hog' (noun). The typical construction is

[adjectival noun* - the thing that they are dominating] [hog as a noun].

For example, someone who takes more than their fair share of the road when driving is a 'road hog'. Someone who sleeps on more than half the bed is a 'bed hog'.

You can use this as a verb - 'They were hogging all the covers'.

Although the OP requested an adjective, there is not one, at least informally - we would not call such a person 'hoggy' or 'hoggish'. (We would call them inconsiderate or selfish, but these are more formal terms.)

The term "bogart" is especially connected with someone who takes more than their share of illicit drugs which are meant to be shared equitably or communally. However, those within drug culture can apply it to any scarce resource that is unfairly monopolized. The more common use is as a verb ('don't bogart that joint, man, pass it around') but it can also be used as a noun, 'He's such a bogart with his stash'.

https://www.dictionary.com/browse/hog

noun (3) a selfish, gluttonous, or filthy person.
verb (used with object), hogged, hog·ging. to appropriate selfishly; take more than one's share of.

https://www.dictionary.com/browse/bogart?s=t

verb (used with object). to take an unfair share of (something); keep for oneself instead of sharing:
verb (used without object). to act or move in a tough or aggressive way: That big guy doesn't ask--he just bogarts.
noun. a person who hogs or monopolizes something.

*also called noun modifiers or attributive nouns.

A slacker.

a person who shirks work or obligation

MW

This word does have some camp meanings, but, still, ...