Well Actually, Tyranitar would pick up an easy win over Aggron. Well its not because of the typings, the looks, its about the stats.
1st of all, Tyranitar is a pseudo-legendary Pokemon that has a total stats of 600 compared to Aggron with 530.
Well yeah its because of defense that Aggron is a freight-train and so Tyranitar is, but speed is what makes Tyranitar a colossus and a monster.
How about you try to a lvl 100 Tyranitar against a lvl 100 Aggron.Tyranitar has the speed everytime so T-Tar will OH-KO Aggron with earthquake. Tyranitar can always outmatched and overpowered Aggron, no doubt. Tyranitar is a pseudo-legendary, plus has better stats than aggron.
.. oh yeah I forgot, T-Tar can also OH-KO Aggron with a fighting type move because a almost fighting type moves are physical and T-Tar has a monstrous attack stats that can make a physical attack very strong.