Here are 3 primary sources that illustrate how dragons were perceived during the Renaissance. As you can see, each of these paintings shows the dragon as something to be afraid of or something extremely powerful.
St. George and the Dragon (by Gustave Moreau)
This painting is probably the most popular depiction of the St. George story. It's clearly showing the bravery and valor of St. George, attacking a beast that's apparently trying to hurt him. Just the pose and facial expression that St. George has perfectly summarizes the Renaissance's attitude toward dragons.
Dragon Attacking Lion (by Leonardo DaVinci)
This is probably my personal favorite dragon image. Why? Because one of the most fearsome predators know to man, the lion, is about to be mauled by something even more terrifying than itself. I think that was the whole point of this drawing was just to show that dragons were something powerful and respected.
Two Followers of Cadmus Devoured by a Dragon (by Cornelis Corneliszoon van Haarlem, 1588)
This gruesome episode comes from the story of Cadmus which is told in Ovid's 'Metamorphoses'. Cadmus was sent by the Delphic oracle to follow a cow and build a town where it sank from exhaustion. The cow stopped on the future site of Thebes, and Cadmus, intending to sacrifice it, sent his followers to get water from the neighbouring well of Ares. They were killed by the guardian of the well, a dragon who was the son of Ares. Cadmus then killed the dragon and on the advice of Athena sowed its teeth in the ground, from which sprang up armed men who slew each other, with the exception of five who became the ancestors of the Thebans. Again, the intention of the way the dragon is shown here seems to be spark fear of it and know that it's something not to be contested.