My examples:
(1) Caliban. Horrible gun handling, can't hit shit, can't sidescrape, but if a Caliban is on the enemy side no one dares to charge unless he's confirmed reloading. Also Caliban can't push or hold the first line. Basically decreases the team's offensive capability.
(2) Iron Arnie. Low HP pool, can't sidescrape, big cupola, getting targeted by arta all the fucking time, low DPM, but playing against it is also nightmare, it has got 300 pen HEAT and a stronk turret with only cupola and the neck shot trap weak spots. Also this shit is immune to HEAT. This one is good for the team though, except when the opponent has 3 bourrasque and your team got 3 iron arnie which is extremely rare.
(3) FV304. No explanation anymore. Can't hit shit if they move but getting targeted by one is nightmare annoying. Teammates complain why it can't stun, tank owner complain why it can't hit shit, opponents complain why it's so annoying.
(4) Italian TDs when redline camping. Poor accuracy and pen can't hit shit, but the attacking team can't pen it from 400 m either. It basically drags the battle into a stalemate unless one side has absolute numerical superiority. This one is obvious, teammates angry, opponents frustrated, tank driver either bored to death or miss every single shot.
(5) StuG IV. This shit is just a worse Stug III G in every single aspect but its owners are generally decently skilled so also feels bad to play against. High chance of APCR spam. Also not a big HP pool to farm off.
(6) BatChat 155 58. Do I still need to explain? Getting hit three times for barely 300 damage combined but stunned almost for a full minute.