From 2006

I did a random search of the New York Times to see how people were using the word “nemesis”

• The Los Angeles Lakers Kobe Bryant is quoted as saying the third quarter of their games this season has been their nemesis.
• Kristanna Loken, is said to be Arnold Schwarzenegger’s nemesis in Terminator 3.
• The French prime minister, Dominique de Villepin is said to have a nemesis in his own Interior Minister Nicolas Sarkozy.

All these usages line up well with the dictionary definitions I turned up.  To use The New Oxford American Dictionary as an example, a nemesis is

“the inescapable…agent of someone’s…downfall.”

The OED tells me that this word comes from ancient Greek where Nemesis was a goddess.  Her job was to keep an eye out for people who were being overly successful, particularly when the success is undeserved and even more so when it is ill gotten.

She is the goddess of righteous anger; divine retribution and vengeance, but only where vengeance is actually fair in balance.

In the pantheon of ancient gods she appears to me to be unusually reasonable.

Her name is said to translate as “to give what is due.”  She’s the daughter of night, or at least the goddess Nyx and is still said by some to have evaded the advances of Zeus.

I’m liking her more all the time.

I see that the entrys in the OED second and draft third edition are a little different.  They have pushed the date of the first citation back by 25 years or so to 1542 and there are several more subtle varieties of definition in there.  But the new entry I like the most relates to astronomy.

In 1984 in the journal Nature, a paper by Davis, Hut & Muller proposed a twin star to our sun as a possible explanation for an apparent cycle of mass extinctions on earth that seemed to show up every 26 million years.  Their theory was that the orbit of this star every 26 million years moved into an area called the Oort cloud and dislodged comets that then pounded the earth.

However unjust this may be, they suggested that if and when this companion star is found, it be named NEMESIS.

Isaac Asimov wrote a book on the idea.

In the 20 odd years since, nobody has found this theoretical star and the idea that extinctions come and go every 26 million years is also up in the air.  But the OED citation shows a certain sense of humor about it that originates with the authors of the theory Davis, Hut & Muller; they go on to say

“We worry that if the companion is not found, this paper will be our nemesis.”