We do see Jehova doing things some would consider "not nice" in the OT, like proclaiming judgements and warnings, forcefully coercing people to do things, wiping out civilizations, and killing people for disobeying him. He was (and is) merciful, though- it just doesn't stick out as much as the punishing and killing.
Jesus didn't do those things, because he was setting an example for us- while God's wrath is pure and righteous, the wrath of man isn't. So Jesus didnt do anything we aren't supposed to do. He did preach the wrath of god, though, and warned people about sin.
When Paul tells Timothy "all scripture" is good- he is referring specifically to the OT, because the NT wasn't made at the time. The OT scriptures are full of testimony about Jesus, and you can learn many principles that are still applicable to life today from the OT.