The "man of sin" is mentioned under other names in other passages as well, in Daniel 9, & Rev. 13. I believe his coming to power will be the beginning of the eschatological events.
Many people have mentioned many candidates for that office, from Nero to Attila to Alexander The Great, to Napoleon to Hitler to Stalin to Pol Pot to every pope to Donald Trump. But NONE has met ALL the criteria Scripture assigns to that man.
Let's look, for example, at Nero. Yes, he was a very bad boy. Yes, he ruled the Roman empire. Yes, he killed a number of Christians, including Paul. But.....
He didn't overthrow 3 other rulers to become Caesar. He was APPOINTED to office.
He was never in Jerusalem, so he couldn't've committed the AOL. And he worshipped the Roman pantheon of gods/goddesses.
He was overcome by man, specifically General Galba.
He was not cast alive into the lake of fire; he DIED in fronta witnesses after having his secretary stab him.
And, he had no miracle-working false prophet as his deputy.
The TRUE "man of sin" MUST meet EVERY Scriptural criterion written about him, to the letter. So far, that hasn't yet happened.