Well, there's a Level 80 Simius Tyrant but it has only 365,821 HP. What, I like to be specific! But getting back to Telethia, which has 10,137,600 HP, it has the same resistance to every attack, so it is down to having strong Skells, skills that boost Skell damage, and ALL the Ultrafauna augments you can afford, to deal more damage and make things easier.