Another old British expression referring to doing something to make an agreement go wrong is to "queer a deal." Not a sexual orientation reference, but an indication that something has gone wrong. Of course, that goes with the implication of the sexual orientation usage suggesting that someone's sexual preferences have "gone wrong." Another reason to avoid use of the word "queer" today.

Historically the term "nigger" was derived from the Latin, "niger" meaning black. There is a river of that name in Africa; a country named "Nigeria"; "Negro" is also drived from the same Latin root. So, black = niger = nigger. Technically, if you call someone "nigger" you are simply calling them "black." Mark Twain used "nigger" repeatedly in his classic "Huckleberry Finn" novel with (I believe) no malice of intent. But today, the N-word carries substantial additional baggage.

I once worked for a Greek fellow whose worst insult (often used) was to call someone a "Turk."

This all goes to the idea expressed above that the insult is in the intent and/or the perception, not the word itself.