Lethal Joke characters are characters who are intentionally designed to be bad or otherwise unreliable by the creators, but with a bit of planning and skill on the player's part, become genuinely powerful or threatening.
Jigglypuff: the Smash Bros series.
-Jigglypuff is one of the easiest characters to kill, has no ranged options, slow mobility, and several of her moves leave her extremely vulnerable to counterattack. Her most infamous ability is "Rest", which causes her to fall asleep. Rest also does a ludicrous amount of damage/launch to anyone within range. That range? literally touching her. This essentially means that using rest is just as likely to get her killed as it is an opponent. Other moves, like "pound" are a pitiful jab to her left or right--except that jab also halts her descent, allowing for a surprising amount of aerial control. She's terrible, but in the right hands is capable of handing out embarrassing losses like candy.
Antiquarian: Darkest Dungeon.
-the antiquarian is something of a utility character. All of her abilities (seem like they) are complete dogshit, having names like "Get Down!" "Protect me!" and "Nervous Stab" (the icon for which shows a kukri... which isnt a stabbing weapon lol). Her only real use is that bringing her allows you to carry more gold and find special "antiques" worth even more gold, so she's only good for farming. Her health and damage are unimpressive, and her Dodge is alright so at least she *might* not get obliterated instantly... except im not being entirely honest. "Invigorating Vapors" applies a 10% (additive, so 50%+10%=60%, not 55%) to your entire party for 3 rounds. It also stacks with itself. The optimal use for Antiquarian is to have her swing her censer around and force your team to vape every single turn for a whopping 30% dodge bonus. An enemy with a 90% accuracy targeting your guy with 35% dodge will suddenly end up with only a 1 in 4 chance to actually fucking hit the guy in the first place. This can outright trivialize the difficulty of any longer, endurance based fight. She also possesses the unique ability to force others to guard her (taking hits for her) which when used on an ally that can counterattack, doubles the amount of counters theyll get while making them difficult to hit in the first place. used on, say, a Highwayman, an enemy team will just take itself out by proccing ripostes.
Conviction: Arknights
-Conviction is an april fools operator released in tower defense game, Arknights. They were given out for free, and are obviously a joke. their art style is distinctly more anime than the rest of the characters, their gender is listed as "Conviction" in their file, and they stun themselves for 10 seconds when you deploy them. Both of their skills are both gambling based as well, their first only doing double damage to a single target... but with a 5% chance of doing *800%* instead. their second does a solid amount of damage in a radius around them and also shuts down enemy passive abilities for 4 seconds--an actually strong and useful effect... but it has a 50% chance of instead hitting your allies and stunning them rather than just silencing them. Whoops. With a bit of luck and some buffs from allies, that 5% chance hit can absolutely obliterate whatever theyre fighting... but uh, dont count on it.
Meepo: Dota 2
-Meepo is infamous for being borderline impossible to actually play. Hes a silly farmer fighting gods and extradimensional beings, and his abilities all suck pretty bad. What makes him special is his ultimate, which permanently spawns 1-3 copies of him. they dont get any of his items besides his boots and so their stats are terrible, but they all have their own cooldowns and similarly shitty abilities. Theres also a catch: killing any meepo kills all of them. This makes playing him extremely intensive as you switch control between independent Meepos, none of which can actually 1v1 pretty much anyone. Actually seeing a Meepo be played is rare, and usually a sign that person is throwing. He isn't actually weak, strictly speaking. he can be in multiple places at once, farming different camps and helps out his entire team at once, its just that Dota 2 is already a game that requires a ton of attention and map awareness and game sense and reaction time, so the "Lethal" part demands so much skill that most pro players dont even bother with him--its just easier to get value out of other characters