Karma is a bitter pill (to swallow) Something that is very unpleasant or difficult.

Hello, you can change the word but you will of course change the meaning! But also, no you can't because it's a fixed phrase of sorts. Bitch has specific connotations, it will convey a slightly different idea than "Karma is a bastard" let's say. So think about what is the message you want to communicate. Using swear words, would imply that 'karma' enjoys getting its own back, and is a little heartless (well at least to me). BTW we have a common phrase for the same basic idea that is completely acceptable, it is "what goes around, comes around". So what you send into the round world, will fly right round and come back to you. This, unlike your original sentence perhaps, could be used in a positive way. EG I always help my friends because I reckon what goes around comes around. Although to be honest we normally mean it from negative actions. Possible options, all NonStandard, my inventions off the top of my head! Karma is blind Karma is heartless Karma is an angry jilted lover

Not really, the English languages uses the word "bitch" very often in many situations to describe. Something that can be irritating/frustrating/annoying/unwanted etc. Why we use "a Female dog" I am not really sure. It may have something to do with pet owners or dog breeders not wishing their bitch to become impregnated by a stray dog, when on "heat". Or it may be related to a female dogs behaviour. Although female dogs are generally considered to be the better more loyal and obedient pets. The English language is weird. P.S bitches do not exist only amongst the dog family, you can have bitches in other animal species.