The German compound word Chancentod combines the French "chance" with the German "Tod" (death). The pejorative is most commonly used in the context of sports, in particular association football (soccer). Directly translated as "death of chances," the best English equivalent might be "opportunity killer".
The noun refers to a player, most commonly a striker or an attacking midfielder, who misses a lot of good opportunities, i.e. makes a lot of attempts at the goal without scoring. Note that the "title" of Chancentod, in its milder form, is earned over the course of a match - if a player simply has a bad day. The harsher variant sees the player "build up" a reputation of missing a lot of chances over a season, or even an entire career.
It's remarkable about the term that, despite its derogatory meaning, it seems that fans use it to refer to a player on their own team at least as frequently as to players on opposing teams (of which there are a lot more). The term therefore also may be considered to be a stand-in for "attacking player (on my team) that I don't like."