In the melting pot that is American English, Yiddish has contributed considerably to the alchemy of the language. And while the oldest Jewish congregation was founded in New York in 1654, Jewish immigration to the United States was small until the 1880s. After that it was relatively high until choked off by the 1925 restrictions designed to limit ethnically undesirable immigrants. Jews had already established flourishing communities in the interim, however, and were busy speaking, writing, and publishing in their own melting-pot language, which combined influences from Hebrew, German, and other European languages. For the past 130 years, Yiddish has given America a rainbow of fun, silly, and just plain useful terms.
A surprisingly large number of English words from Yiddish are devoted to insulting name-calling. In fact, there are so many insults that I had to break it down into categories and subcategories. Consider the following:
People Worthy of Your Scorn
schlub: a stupid, worthless, or unattractive person (from the Yiddish zhlob or zhlub meaning yokel or boor; Merriam-Webster‘s online, hereafter M-W).
schmegeggy: a contemptible person, an idiot (Oxford English Dictionary online, hereafter OED).
shmendrik: a contemptible, foolish, or immature person (the name of a character in an operetta by Yiddish-language playwright Abraham Goldfaden; OED).
schmo: an idiot, a fool (delightfully described in the OED as “a person who stands watching a machine make doughnuts, and  cannot understand the process,  cannot get up will power to leave”).
schnook: a dupe, a sucker; a simpleton, a dope; a pitiful wretch (OED).
Subcategory: Everyone Else
klutz: a clumsy person (from the Yiddish for “wooden beam,” from Middle High German kloz meaning “lumpy mass”; M-W).
nebbish: a timid, meek, or ineffectual person. Note that this is a noun, not an adjective (M-W).
pisher: a young, inexperienced, or insignificant person (OED).
schlemiel: an unlucky bungler; a chump (M-W). See “schlimazel” below.
schlimazel: a consistently unlucky, accident-prone person, a “born loser” (OED). The classical explanation of this idiomatic idea is that the schlemiel chronically spills the soup, but the schlimazel is the one the soup always seems to get spilled on.
People Who Complain
noodge: a person who persistently complains or nags; a pest, a bore (OED).
kvetch: a habitual complainer (from the Yiddish kvetshn, literally, to squeeze or pinch, from Middle High German quetsche; M-W). Note that this is more often used as a verb.
People Who Are Interpersonally Annoying
nudnik: a person who is a bore or nuisance (from Polish nudzić, from nuda boredom; M-W).
schmuck: a jerk; literally, penis (M-W).
schnorrer: a beggar, especially one who wheedles others into supplying his wants (M-W).
People Who Infuriate You
ganef or gonif: a thief, a rascal (from the Hebrew gannābh, also meaning thief; M-W)
mamzer: a bastard (both literally and figuratively; OED). A mamzer is clever at dishonestly turning things to his own advantage.
meshuggener: a foolish or crazy person (M-W).
People Who Infuriate You in a Seriously Non-PC Way
schvartze: a depreciative term for a black man (OED).
shiksa: a derogatory word for a non-Jewish woman (or, in moments of internecine nastiness, Orthodox people also use it for Jewish females who do not follow Jewish precepts). This comes from the Hebrew word for “blemish” or “abomination” (M-W).
People Doing the Name-Calling (i.e., Gossips)
kibitzer: one who looks on and often offers unwanted advice or comment, or, in general, voices opinions (M-W).
yenta: one that meddles; a blabbermouth, a gossip. This descends from the first name Yente (M-W).