Oh, I see. I misunderstood.
I find Germanicus to be a little overrated-his early death allowed his supporters to kind of dictate the narrative on what his character would be, and contrast him with a very much disliked Tiberius and Caligula. He seemed to have been hotheaded himself and I think the jury is still out on his command ability-he did very nearly fall into a second Teutoburg Forest after all. I'm also not sure everything would be rosy between him and the senate either.
Plus it's hard not to avoid the feeling that his wife Agrippina the Elder was a Lady Macbeth-style schemer who, like her husband, got a free pass thanks to having Tiberius for an enemy. (And I remain convinced she was the motive force behind Germanicus' mysterious trip to Egypt, based on the fact that Germanicus scampered the moment Tiberius politely told him to...)
Honestly, it's hard not to sympathize Tiberius as regards those two--it's bad enough for a royal to face plotting relatives--it's worse to face popular, incompetent plotting relatives, because they blame you for their own screw-ups...