Also, forgot Manx leaders.
You only have two real choices, both male, both badass, but neither entirely appropriate as they were never actual leaders. However, in the case of Man, I think you're going to have to be flexible.
The first is Wimund. He was the son of the Duke of Moray, the first Bishop of Sodor and Man (the seat of the Diocese was on The Isle of Skye, however, but Man was under See), and he was an absolutely craycray Herculean Bishop Prince Warrior. Basically, he visited the Isle of Man as a monk, and was so hunkalicious and oratorial he persuaded the Islanders to make him their Bishop. As soon as he was ordained, told them he was the heir of a Scottish dukedom and raised an army to take it back. He and his men went fully fledged Viking crazy, and travelled through the Isles raping and murdering and looting their little hearts out. When the people in charge of this kind of thing had enough of him, they both blinded and castrated him, but he was such a badass that he didn't die so they had to lock him in a monastery for the rest of him life. A rather disparaging source of this legend can be found
here.
The other choice is Illiam Dhone. He led a Manx nationalist rebellion against the Lord of Man during the English Civil war. Actually, he led the rebellion against the Lady of Man, the Lady Derby, because the Earl of Derby was imprisoned by the Parliamentarians in England. Once the Parliamentarians had landed on Man, the Lady tried to sell them the island in exchange for her husband's freedom. This, unsurprisingly, rather pissed off the Manx and they rose up against her, stormed the forts, and secured the Isle of Man, and by default a Parliamentary victory. Dhone then negotiated the island's sovereignty with Parliament and as a reward was later made the Governor of the Isle of Man. When the monarchy was restored in 1660, he was accused of some trumped up money laundering charge, and was eventually executed by the Crown for not being their b'hitch. Source
here.
Personally, I'd love to see a Wimund leader screen, but in all honesty Illiam Dhone is probably a more appropriate choice. Unless you want an ancient-medieval leader, in which case, I can't help you and
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