The hero of the Harry Potter series isn't as flawless as many presume.
Fans of the Harry Potter series undoubtedly adore the talented, courageous, and kind wizard. Throughout the films and books, Harry Potter's intellect saves the world from the Dark Lord Voldemort. However, Harry's 'accomplishments' cannot conceal the fact that he often makes mistakes. Not only ordinary errors but sometimes Harry commits unimaginable acts, causing harm or consequences to others.
1. Terribly mistreating his date at the Yule Ball

One of the moments when Harry Potter's attitude was utterly repulsive, which viewers despised the most, was during the Yule Ball in the fourth installment. Unable to invite Cho Chang and Ron unable to invite Hermione, they resorted to the 'backup plan' of inviting Parvati and Padma. Throughout the ball, the two treated their partners abominably, even ignoring them.
Not only were Parvati and Padma mistreated at the Yule Ball, but even Hermione was hurt by these two gentlemen.
Refusal to heed Dumbledore and Snape led to the demise of Sirius.

Due to Harry's ability to infiltrate Voldemort's mind, Professor Dumbledore tasked Snape with teaching Harry Occlumency to 'shield' his mind. However, not only did Harry refuse to listen to Snape, but he also attempted to pry into Voldemort's thoughts.
As a result, Harry and his companions fell into Voldemort's trap at the Ministry of Magic. In that confrontation, Sirius Black perished. It all stemmed from Harry's refusal to heed both Dumbledore and Snape's instructions.
Boldly using spells during the '7 Potter' battle.
To ensure Harry's safe passage, the Order of the Phoenix devised a clever plan: consuming Polyjuice Potion to become 7 Harry Potters. This way, the Death Eaters couldn't identify the real Potter to attack.

During transit, Harry noticed Stan Shunpike— the ticket conductor from the fifth installment—fighting alongside Voldemort's cohorts. Without hesitation, Harry cast Expelliarmus to disarm him. Unfortunately, this action revealed the real Harry to everyone.
As Voldemort previously pointed out, the Disarming Charm is Harry's most 'distinctive' spell. Consequently, Harry and Hagrid became targets, leading to the collapse of the entire Order of the Phoenix's plan.
Employing a lethal spell on Draco and leaving the victim bleeding dangerously?

Sectumsempra, a spell invented by Professor Snape and documented in his book 'Advanced Potion-Making,' later fell into Harry's possession. Upon encountering this spell, Harry recklessly cast it on Draco without understanding its consequences. As a result, Draco suffered a severe cut. Not stopping there, Harry... left Draco bleeding profusely. Draco could only survive by seeking help. Among all the deeds Harry has done, this is undoubtedly the most cruel.
Image Source: Warner Bros.