User blog comment:Wrath022/Chapter 516: The Truth About Enchantment, Review/@comment-4507125-20161231163540/@comment-23853100-20170101042236

There's some doubts on becoming violent and aggressive part actually.

Irene only became aggressive when her husband tried to harm her child, it's more to wanting to protect her child over being violent and aggressive. Even the current Irene isn't really violent or aggressive. It's more to her desire for a human body which is now pure uncontrollable greed, made her deranged enough to destroy any obstacle that blocks her from obtaining a normal human body back. She didn't even seem to have second thoughts taking over Wendy's body.

Laxus was a case of pent-up frustration over constantly being compared with Makarov and his father getting exiled from the guild. Add Laxus' refusal to open up and accept his guild mates who he deemed as "weak", it was a matter of times before pent-up negative emotions explodes out.

Cobra was just following orders, God Serena is an idiot. The "true" Dragon Slayers hasn't really shown any signs of real violent or aggressiveness.

Yes i know Natsu constantly start a fight or brawl in his guild but that's more to friendly brawl over actually being violent and aggressive. Natsu is just a simpleton who loves to fight after all. Natsu himself even said it to Lucy at the start of the war against Alvarez, he likes to fight not kill. Sting showed it once against Jiemma when he thought Lector died but that's just anger and shock controlling him temporarily. Sting himself didn't really become a violent and aggressive person.

And the other example Acnologia is a huge mystery. We don't know a thing about his past.

In short all the so called aggressive and violent symptoms we have seen up to now is purely human emotions over really turning violent and aggressive. Especially if we compare it to people like Zero and Zancrow.