Thief: Not that I'm complaining about it, but...HOW DO YOU MISS A VOLCANO?!
Earlier, when they were captured, BM tried to kill his allies. It was in a small corridor, easy to hit them in, with reflecting walls. What happened? He hit something: himself. It was the same attack as the volcano. He had no way of knowing that Princess Sara had cast a Wall spell on their cell.
Red Mage: How did you not only manage to miss us, but also hit yourself?
Due to Red Mage's unfailing belief the world works like a Tabletop RPG, this occasionally comes up for him, too.
Black Mage: You pushed Red Mage [...] Onto Fighter's sword. Fighter: Which is weird because it started out sheathed. Red Mage: I botched my Athletic Roll...Big time...
The strip has, among other delightful slices of Gamer Life and other nerd instances, the occasional example of truly epic fail, almost always by Lewis. Though he is usually a victim of his own impulses and poor planning, he is also cursed with truly awful dice luck. This is a decent example of how bad Lewis can roll. He has also jinxed a die so badly it infected other d20 with the "1" virus, rolled a "1" when it was buried, and started making "1" show up everywhere. Further, Williams even has a collection of Nerdity out titled the Big Book of Epic Fail.
In one Lewis tries to achieve godhood through demonstration of his miraculous bad luck.
Matt from Murphy's Law did this on his Test of Hidden Traps.
In the first book of Goblins, Fumbles fumbles a to-hit roll spectacularly. He trips, sends his spears flying into a lantern, which sets a hut on fire, which sets a bird on fire, and said bird retaliates by gouging the hell out of Fumbles' head.
Forgath: I just wanna know what kind of fumble chart he's using, so I could avoid it.
In a non-canon Problem Sleuthdonation page, Team Sleuth strikes back at the Midnight Crew with the insanely powerful Catenative Doomsday Dice Cascader, a weapon that calculates damage by rolling a die for result X, and filling the remaining popomatic bubbles with additional X-sided dice. This is repeated until all dice are rolled, with the final die determining damage. The final result? One. Out of 50 trillion.
Freefall: Helix managed to blow out a bulkhead on the spacecraft he and Sam use. While making microwave popcorn, no less.
Cosette from Questionable Content has a habit of this. First, she worked up the courage to ask Marten out only to find he had a girlfriend, then went to the coffee shop said girlfriend owned and ended up complaining to her about it, and then ended up being the waitress that served the two later that evening. Later, Marten attempted to set her up with his friend Steve, and she didn't call because she accidentally fell down the stairs while ogling his picture, and when they finally got together, their first date lovemaking was interrupted by a fire drill and then a pop in her injured neck, and when she sought a job at Coffee of Doom, it turned out that every past business she worked for shut down under less-than-reputable circumstances, from burning down, to the owners being arrested for criminal activity. It leads characters to believing that she's cursed to cause Epic Fail in those around her as well.
Stef Murky of User Friendly is absolutely awful at video games. He once fell in the lava in Neverwinter Nights (something not possible without modding the game) and also once fell in the lava at the startup screen of Quake II.
Cleo from Bobwhite discusses this. While her dad tries to teach her how to fold clothes, Cleo talks about how funny it would be if her terrible clothes-folding skills accidentally set her clothes on fire.
Thog failed his will save against a Zone of Truth spell (which normally only prevents telling lies) so badly that he started spouting every truth he knew, resulting in several Too Much Information moments.
The image for Failed a Spot Check is their most exceptional example of this failure. Elan identifies a room as a safe place to sleep, missing the horde of goblin ninjas who weren't even bothering to hide.
The Ho'aku tribe was truly an epic fail, filled with a) weak and easily influenced members, b) jealous and power-hungry contestants who wanted to lead and voted out the first two leaders, and c) Russell Hantz, who sabotaged their tribe. What happened was one of the worst losing streaks in the comic's history, with the Ho'aku tribe losing ten out of thirteen challenges, going to every single Tribal Council but one, and ultimately being whittled down to two members. However, the tribe's plight is spectacularly subverted when a member of the Ho'aku tribe manages to go on an immunity run and win the game!
Cherman from Season 9 was an epic fail in all challenges, in spite of being a robot specifically programmed to be the ultimate Survivor bot. Then it's similarly subverted at the very end when he wins the entire game.
An unwise decision in one session of the game Sburb had consequences so staggering they rendered someone else's session unwinnable.
It later turns out someone in the latter session, all by themselves, managed to make both sessions unwinnable by giving a universe cancer. Fails don't get much more Epic than this.
Eridan's entire session in the Land of Wrath and Angels was wasted due to his determination to kill the friendly yet formidable angels until he finally turns them all against him. Everyone he complains to about it figures out that they aren't the enemies, but he continues to whine about its unfairness long after the game is over.
There's a ton of examples from VG Cats. In one comic, Leo (who is Altair from Assassin's Creed) tries to pick his nose, only to stab himself in the face with the hidden blade.
Final Fantasy VII: The Sevening: Without materia, Cloud can't even enter a house properly. Instead, he somehow winds up getting knocked over and pinned down by several cats. Even he doesn't know how it happened.
In "Drunk Driving With Tora" (which provides the image for this subpage), Tora Tsukino takes the main page image Up to Eleven by crashing the Tsukinos' car into their house. Which is several stories above ground in a high-rise apartment.
The roleplay for "Scaredy fox training" reveals that some time after the "Inu and Uma Bio" roleplay, Miles "Tails" Prower (yes, that one) attempted to repair a clock for the Mokarys... and instead wound up creating a poltergeist, which promptly started haunting the house. That's right, he somehow managed to make a poltergeist out of a clock. Completely by accident. And this is Tails we're talking about, not some hapless Walking Techbane with no idea how clocks work, making the fail doubly impressive. (It's later implied that the clock was magically sabotaged by Mysto with the intention of making a Yandere who would slaughter Miriam.)
The rookie adventurers in the "Binwin's Minions" segment of Table Titans manage to suffer a total party kill, entirely through their own incompetence, during their first job interview.
In Ansem Retort, Sora participated in a Vice Gubernatorial debate against Owl from Winnie the Pooh. Owl didn't speak English. And halfway through the debate, Red XIII killed Owl. Sora not only continued to debate Owl's corpse, but somehow managed to lose to it.
Gunnerkrigg Court: Annie's friends take her bowling and she hits the gutter four times in a row. This gets her so angry that on the next page she uses her powers to throw the ball so hard that it bursts into flame... only for it to land, scorched, in gutter, again. The gang recommends switching to another lane, because the current one is on fire.
In Concerned, protagonist Gordon Frohman is prone to comedic failure that sometimes reaches this level. For example, he tries to sabotage the City 17resistance by pretending to order a shipment of weapons, while making over-the-top Suspiciously Specific Denials that he's just randomly tapping keys on a keyboard and lying about it. Instead, he manages to actually order a shipment of weapons, exactly as he said he would.
Luke of One Piece: Grand Line 3.5 intentionally invokes this trope every time he has to roll for a form of social skill check. He does so using a d20 with nothing but 1 on it.
Yeon Yihwa in Tower of God uses powerful fire magic, but she reallycan't control it. A Funny Background Event in one panel has her dropping her drink because it's on fire. Soon after that, she's trying to practice by burning a match with her mind, and she manages to burn the whole rest of the room without touching the match.
Lil Char and the Gang: Charmander somehow manages to lose at chess to Bulbasaur, who doesn't understand the rules of the game and spends most of the time eating the pieces.