I heard Japanese has no swearwords, no bad words of any kind. The closest is 'bakadesu' (however you spell that) which is just a weak version of 'idiot'.

Is this really true? Doesn't seem natural.

Swearing in Japanese

http://www.insultmonger.com/swearing/japanese.htm

Yeah, Japanese swear words don't really compare to other cultures. Like some stuff I hear in English is god awful, but the worst thing in Japanese is slut. I've heard some "bad" ones and asked what it meant and they'd be like "means bad person".

Looking through Itk's list there don't seem like much missing!

thats not what i heard. unless these subbed animes are lying lol. because ive seen "bastard" "fukn little $hit"...

Yes, those subbed animes are lying. There is no expression in Japanese that equates to the English "fu-kin' little $hit" or "bastard" (at least not in its vulgar sense; there is, of course, a formal/legal word in Japanese that means "a child born out of wedlock").

If you want to offend someone in Japanese, the most efficient way would be to speak without any formalities.

learn something new everyday...well every other day.

What about Yaro, Kisama, Jiji, Yourou, Onore from Itk's list?

hoho, ever try that with someone above you like a teacher? instant ruler on the wrist.

The only one of those that might approximate the vulgar sense of "bastard" is yarou (And what is yourou? Is that a mistake for yarou?), but the Chinese characters that are sometimes used to write this word (characters that literally mean "field-boy") did not necessarily ever imply "bastard"; as far as I know, they were just chosen for their onyomi phonetic values, and they actually represent some Japanese word that is the masculine equivalent to the old-fashioned word for "girl; young woman," i.e. merau > merou. So, the common Japanese expression of anger, kono yarou!, probably means nothing more than "this guy!"

As for the rest of the identifiable Japanese words from your list, kisama is literally an honorific expression for addressing a nobleman (something like "Your Honor" or "Your Highness"), jijii just means "grandpa" (also in the sense of "old man"), and onore is a word that originally means "oneself," but at various times in Japanese history and in various dialects has been used as a personal pronoun, meaning either "you" or "I."

hahaha, I could imagine it clear in my head, talking to older person with futsukei form

Thanks for the explanation.