Drago and Pitch have a lot in common. They are both black-haired villains who tried to overthrow a group of people(the Hairy Hooligan Tribe and the Guardians); they are sadistic, cynical and brutal; they both control powerful creatures(such as Nightmares and dragons); and they have both killed a character close to the hero(Sandman for Jack, and Stoick for Hiccup), although Drago was more successful than Pitch in this goal, since Sandman was restored to life at the end of Rise of the Guardians. In addition, both are villains who have been defeated when the very forces they sought to control turned against them- both the dragons Drago enslaved with his Bewilderbeast and the Nightmares Pitch used to control. Drago himself has said that "I know what it is to live in fear", so the odds are great that he could be able to see Pitch and interact with him. Pitch would see great potential in Drago as a means of inspiring fear in people and controlling them as well, although Pitch's method in gaining supporters is more cunning than Drago's since Pitch is more seductive and manipulative, whereas Drago is assertive and dominating. The two villains alongside one another make a serious threat to both Berk and the Guardians.
After hearing about him from Astrid, Drago seems to acknowledge Hiccup as a rival of sorts, realizing that another dragon-tamer could endanger his monopoly over the dragons. A parallel of sorts to Hiccup, given his own mastery over legions of dragons. Drago is a stark contrast to him as well, using abuse and force to dominate the will of his dragons as opposed to befriending them. When the two finally face off, Drago, identifying Hiccup upon seeing him ride his Night Fury, Toothless, seems amused that his reputed nemesis was little more than a boy, seemingly dismissing the threat that Hiccup posed. While Hiccup still believed that Drago could be reasoned with, he proves otherwise, stating that strength of will was true power and the only way to control dragons -- an ideal he demonstrates by commanding his grey Bewilderbeast to take control of Toothless, and using him to kill Hiccup. Though this fails due to Stoick's intervention, it succeeds in shaking Hiccup's resolve. Drago then takes Toothless as his mount to further demoralize Hiccup.
During Drago's invasion of Berk, Hiccup continues to surprise him when he and his companions show up on the backs of baby dragons, which the Bewilderbeast could not control, then again when Hiccup's bond with Toothless frees him from the Bewilderbeast's command. The tables are turned on the infuriated Drago when Hiccup's ingenuity and Toothless' own willpower rise up against the great and terrible grey Bewilderbeast, shaming both tyrants and releasing the dragons from their control for good.
Friends and AlliesEdit
It is mentioned that he once had a village and a family before dragons destroyed all of them, compelling Drago's vendetta to conquer them. It is possible that he was never very close to them in the first place, as he is clearly doing this simply for the power, hoping to become the "Dragon God".
Drago found the Bewilderbeast as a hatchling during one of his earliest conquests. Drago recognized this as his way to control ALL dragons, whether they like it or not. Drago beat it and even starved it so it was nothing but a huge war machine. He used the Bewilderbeast to kill Valka's Bewilderbeast and then used it to force Toothless to kill Stoick the Vast. In the final invasion, when Toothless challenges the Alpha, Drago loses control and screams "FIGHT!!!" continuously until Toothless blows off its left tusk, and Drago's mechanical arm. Then, it bowed respectively to Toothless, and went back into the ocean with Drago on his back, where, without his other arm, very likely could've drowned.
Just as Valka despises Drago for his cruel and abusive treatment of Dragons, Drago views Valka as his greatest threat prior to finding out about her son, Hiccup, as she was one of the few to stand in his way of complete domination over both man and Dragon kind with her safe haven of Dragons. While he sees her as an obstacle, he also seems extremely confident that his Dragon army and Bewilderbeast tyrant would be able to overpower Valka's own Dragon legion -- many of which were refugees and rescuers, not fighters. His confidence proves to be well-founded when his Bewilderbeast defeats Valka's white king, and he quickly overpowers Valka in battle, her death only being prevented by the intervention of her husband.
Stoick and the other Viking clan leaders turned down Drago when he came to them with his offer of leadership, laughing him away when he demanded that they bow down to him in exchange for safety from the then-threat of Dragons. Seemingly having anticipated this, Drago had several battle-Dragons under his control waiting outside, who then proceeded to burn the longhouse to the ground as Drago escaped. Only Stoick survived the encounter, and he sees Drago as a grave threat. During their eventual showdown at Dragon Mountain, Stoick appears to have the upper hand due to his superior fighting prowess and Drago's disadvantage of his missing arm, and had Stoick not left the fight to come to Valka's rescue, it is possible that he would have defeated the madman then and there. Stoick then intervened when Drago attempts to kill Hiccup by controlling Toothless, taking the death blow intended for his son. Drago barely even acknowledges Stoick's death when he realizes Hiccup was not the one killed, merely smiling and not even turning to look, suggesting both his sense of superiority over the other man as well as a possible realization that the death of Hiccup's father is equally damaging.
Eret served Drago out of fear, before joining the Dragon riders. He gave Eret a symbolic scar for not bringing him enough Dragons. Even when he did, he tried to have Eret executed, both because he supposedly alerted Berk of him and because he outlived his usefulness.