A simple example is the word mierda, or shit. Argentinians tend to use this word casually in conversation. For them, it's vulgar, but not too bad. If something is no good, it's "una mierda". However, in Bolivia, when I dropped this word into conversation, I was told it was considered the height of vulgarity. I was warned not to use it casually.
In Mexico, where I lived for several years, men refer to jerks and assholes as cabrones, the literal meaning of which is cuckolds (for any young Americans reading this, a cuckold is a man whose wife sleeps around behind his back). It's definitely an insult, but Mexican men also use this word quite casually among friends, as we might use "pal" or "buddy" or, among the young, "bro". However, here in Spain, when I used it once in conversation, my friends reacted visibly. They said cabrón is extremely vulgar and insulting here, more so than in Mexico. Be careful with it.
