LoL main champions?

Off-tank, of course. Glass-cannon is an invitation for people to pile up on you and kill you in 1.5 seconds and full tank , although you do better damage than some champions that people tend to make full-tank and are completely useless(like Garen, Renekton or Irelia), u're still nowhere near Nasus level, so you'll still be ignored by your enemies and you'll kind of watch helplessly as your enemy gets squashed and u're left in a 1 vs 3 scenario. I almost invariably use this build: Mercury's Treads, Trinity Force, Warmog's Armor, Wit's End, Atma's Impaler and, of course, one of the three life-steal items because I find building champions like Xin Zhao or Irelia without life-steal is a complete waste. Any one of them works fine, but it is situational. Usually I just go for hydra, cause the splash damage is awesome, but if the enemy team has more than one indestructible brick wall like Malphite, Amumu, Singed, Leona, Alitar, etc, then you absolutely should invest in Blade of the Ruined King. The Blodthirster is for cheap bastards who just want to get pure AD fast, at a lower price than with Ravenous Hydra. It's a decent choice, however. (If you Blade of the Ruined King, you can try swapping out Wit's End for Spirit visage, as you don't really need that much attack speed, given his Battle Cry and the extra health form Spirit Visage does come in handy).

There's another build you can try. Half of it is the same: Wit's End or Spirit Visage again, one of the life-steal items(if you take Spirit Visage and not Wit's End you should always go for BotRK to balance out the attack speed issue) and the shoes. This is where the similarities end, as you get Frozen Mallet instead of Warmog's, Zephyr instead of Trinity Force, and Sunfire Cape instead of Atma's. This is a build I prefer to use on Shyvana, as she needs attack speed more desperately than Xin and her Burnout ability works VERY WELL with Sunfire Cape, but I suppose it's not bad for Xin either.

There's one more build you can try, it's a total bomb in terms of both AD and tankyness, but it doesn't give quite as much attack speed: Wit's End, Mercury's Treads, Black Cleaver, Randuin's Omen, Frozen Mallet and the mandatory life-steal item.

Both of the alternate builds are quite good(even the third one, if you use BotRk), but I prefer the first one almost always because the Sheen effect from Trinity Force is just to good to pass.