In the wilderness, Jesus was "tempted" to do a miracle only God could do : turn a stone into bread. If he couldn't have actually done this, it would not be a temptation.
Jesus verbally made claims on many occasions that he had existed before Abraham which meant he was either a liar or telling the truth..
Jesus prophesied that he had authority to give his life and to raise himself from the dead...and he did just that!
Jesus performed impossible acts of healings, miraculous signs and wonders and raising the dead. Only God could do those acts.
Jesus claimed to be one with God. He claimed to know God intimately and referred to God as Father.
If Jesus was mad, a false prophet or a liar, he would not have been raised from the dead. This proves he was God/from God or at the very least, worth listening to every word and deed he said and done. Everything Jesus teaches in the scripture testaments is worth learning.