Loud, passionate and ridiculously insular to the point of being deluded. Although 16 years in the Championship and League 1 has calmed them down a bit. Paranoid that everything and everyone is out to harm them, which is funny for a club that was lucky to survive being liquidated. If they had been an Italian club they would have had to start again in Serie D, it's as simple as that - the PL/EFL tends to protect the clubs with reputation, they have to save face.
Speaking from personal experience, their travelling fans were always yobs - loud, drunk and obnoxious, always looking for fights (and getting them). This might be seen as a 'standard' of English fans by foreign observers, but there are different levels of it, and it certainly didn't apply to a lot of team's fans. With Leeds it was always huge numbers of morons. They have a thug reputation close to Millwall and West Ham of old, and as such, despite being sportingly irrelevant to many of these clubs, they still have intense rivalries with them. There is also the Lancashire-Yorkshire rivalry with Man Utd, which is originally historical, but more recently stems back to Eric Cantona's signing and the earlier PL battles. In recent times completely irrelevant. Yorkshire people tend to either love or despise them.
Their most famous and successful era of the late 60s into the 70s spawned the "Dirty Leeds" that most opposition clubs and supporters hated because of their brutal style of play. Ironically, many of this stemmed from playing in European matches, including against Juventus, where the dirtier tackling and foul play was picked up on. Over the years the club and fans wore it like a badge of honour, as did some players. More about "Dirty Leeds" and the story behind it here:
https://www.planetfootball.com/in-d...-the-self-fulfilling-prophecy-of-dirty-leeds/
They were always big enough and attractive enough that some random owner was going to come in and give them the backing to get back to the PL one day. First they attracted the idiot Cellino, which failed miserably. They haven't really splashed tonnes of cash (or more than any other top end Championship club - one sale to a PL club can bring in an entire window's worth of signings) but Radrizzani's contacts have been important.
They remind me of Newcastle in lots of ways. Clubs with big and stupid local support that have been financially and sportingly mismanaged horribly over the last 20 years. The Geordies will soon be unbearable with their Saudi cash, but that's a different story. At least Leeds have had to do it the right way in the last 10 years.
If I had to do my top 3 of local fans (from the region), based on experience, who have been the most deluded over the last 20 years then it would comfortably be Liverpool, Leeds and Newcastle. Liverpool have gone from an almost laughing stock to probably the best team in the world, Newcastle are about to be taken over by the Saudis, and Leeds are back in the Premier League. Let the show commence.