The English translation of the first volume of Dungeon translates Main Gauche as "left hand." Although this is the literal French meaning of Main Gauche, in context, it's quite obviously referring to a knife or dagger wielded in the off hand. It shouldn't really be translated anyway, since it's also the English term for such a blade anyway.
The Dutch translation of ElfQuest got particularly horrible somewhere around the Shards War arc: speech bubbles were aimed at the wrong characters, elves were suddenly given new names, and apparently none of the translators had read the original series at all. After five issues or so, the translation suddenly got much better again, and a thank-you note to a Dutch BNF was included on the last page.
Dirty Pair: Run from the Future attempted a Bilingual Bonus, but ended up making several linguistic errors, one of which is hilarious. One of the criminals Kei and Yuri have been assigned to arrest is "Jeannot Delagauchetière", who speaks (what is apparently intended to be) Québécois French. After putting restraints on him, Kei is about to say what he's under arrest for, when he somehow causes Kei's holo-camouflage to deactivate, and reveals that he has several heavy assault mecha under his control. He introduces these mecha by saying "Dis 'Allô' à mes p'tits amis". This literally means "Say hello to my little friends"; the problem is, it has the idiomatic meaning of "Say hello to my boyfriends". Oops! (Another problem is that "allô" is usually only used when answering a telephone call, and "bonjour" would have been the correct choice in this context.)
DC Comics has appearently no one with actual knowledge of the German language on their payroll, since they always rely on some shitty web translator or Write-it-like-you-heard-it when some german pops up. One example is here.
The Polish translation of The Dark Knight Returns is ridiculously terrible: for example, some sentences (including plot-critical ones!) are translated into their exact opposites ("That doesn't make sense" into "That makes sense"); there are also many cases where the translator clearly misread the original (flesh/fresh, sweat/sweet).
One issue of The Simpsons comics has a French taximan say "Coup moi" to Bart. A caption indicates that "Coup moi" is supposed to be a translation of "Bite me". There is 3 problems with that : 1) "Coup" is not a verb, it actually means "a blow" (as in "a blow to the face") ; 2) "Bite me" would be translated literally as "Mords moi" (verb "mordre", 2nd person of the singular of the present imperative) ; 3) "Mords moi" actually does not mean the same thing as "bite me" at all. Given that the purpose of this particular comics was to mock French people, the author could have at least tried to write a correct 2-words sentence in their language.
Transformersself-proclaimed "superstar artist"Pat Lee rendered his name on an old personal website in katakana. The problem? Rather than it being a transliteration of his name, he used a character-replacement font to replace every letter in his name with whichever katakana was under the same key. The result: Michiyamenotehi Funana!
The translation work of the Transformers comics from Titan Magazine in Hungary became something of a Running Joke with its memorable and nonsensical solutions, such as translating "Not on my watch" as "Not onto my wristwatch". The publisher even turned down an offer from the fans when they tried to help out the translators.
The Italian translations have similar errors, usually mistaking a random word for a character's name. Examples include Blazemaster becoming "Bonfire" and Stratosphere being suddendly named "Groundhog".
It's unclear exactly who Marvel goes to for their Arabic, but they're clearly being paid too much. For Apocalypse's backstory, the writers had him be born in the Ancient Middle East and gave him an Arabic name that they wanted to mean "The First One". What they used was "En Sabah Nur", which is a mixed up version of "Sabah En-Nur". "Sabah En-Nur" literally means "morning of light" and is the standard response to the phrase "Sabah Al-Khayr", or "good morning". Even worse, the "En" is really a part of the word "Nur", and it's gibberish on its own. The name means nothing.
In the 1980's, India-based Everest Publications released a series of James Bond comics, which were then sold in Europe. One wonders if for their English translations, they just hired the first guy who walked in and said "shaken, not stirred". The comics included such unforgettable lines as "While 007 in siesta, plane jolted", "good evening, I am giving the sleeping gas" and "don't bother who the room intruder was!"
Remember that the first appearance of Wolverine was in an issue of The Incredible Hulk? Well, in the Norwegian translation of that comic, Wolverine was called Ulvemannen, which literally means "The Wolf Man". Clearly, the translator couldn't even be bothered to look in a dictionary to check if a "wolverine" really is the animal he thought it was. Later Norwegian translators called Wolverine "Jerv", which is the correct translation of his name.
Speaking of Wolverine, early French translations changed his name to Serval. A small, spotted, African feline (admittedly, the French word for wolverine is "glouton", literally glutton).