Barry Allen is one of the most consistently lovable characters in the best of us."
But occasionally even Barry Allen forgets what it means to be a hero. Barry has repeatedly been shown to prioritize his loved ones above all else, sometimes to the world's detriment. He often struggles between letting his emotions get the better of him and being "too noble" to let personal feelings dictate his decisions.
Team Flash Imprisoned Metahumans
Before Iron Heights developed a metahuman prison wing, Team Flash captured and imprisoned the metahumans they fought in the cells of the particle accelerator. Without trial or jury, Barry Allen acted as judge, keeping the metas prisoner for an undecided amount of time until the team could sort out what to do with them.
To make matters worse, Team Flash was always too busy with other things to be much concerned about rehabilitating the criminals, leaving them to mostly rot.
He Attacked His Friends
In season 1, Barry faced a villain dubbed by Team Flash as "Prism," or "Rainbow Raider," who could manipulate emotions. Barry got "whammied" by his powers and lashed out at his friends and loved ones; he lost control of his emotions and the inhibitions he would normally have. He attacked both Eddie and Oliver before Team Flash figured out a way to reverse Prism's powers.
Though most of the effects could be blamed on being "whammied," Barry later itted that it wasn't just the Raider's influence that caused him to act that way. It just gave him a chance to let out the pent-up anger and resentment that was already inside him. Rainbow Raider's powers gave viewers a chance to see for the first time what the Flash might be like if he didn't have his usual moral com.
Becoming "Logical Flash"
After Barry accidentally killed the Speed Force, Team Flash devised a way to make a new, artificial speed force in season 7. Unlike Eobard Thawne's Negative Speed Force, which was fueled by anger and hate, Team Flash made a speed force that would be devoid of emotion; that way it could be safe from personality-altering side effects. With the new speed force, Barry finally gained one of his coolest comic book abilities: speed thinking or "enhanced cognition." Barry was able to mentally solve problems in an instant and see past his emotions to make decisions based on logic.
Unfortunately, Barry also started to lose some of his humanity via his emotions, becoming more cold, distant, and logical. He allowed Caitlin to be injured, psychologically taunted the villain Mirror Mistress, sacrificed their chances of freeing Singh and Kamilla from the Mirrorverse, and pulled Iris out of the Mirrorverse against her will, causing her to suffer severe shock. His actions led the rest of Team Flash to confront him, but he defeated and knocked them out easily. Thankfully, seeing Iris in pain helped to break the Artificial Speed Force's hold on his emotions and he chose to destroy it rather than risk further injuring his team.
Barry Created A Wormhole
In the season 1 finale, Barry agreed with the Reverse-Flash's plan to create a wormhole in order to travel through time and save his mother while returning Thawne to his own time. Barry ultimately decided not to go through with the plan, but his actions had already led to the creation of a wormhole above Central City.
Had it not been for Firestorm and Ronnie Raymond's sacrifice, the singularity would have swallowed the city and killed millions of people. In addition to creating the wormhole, Barry also accidentally created fifty-two breaches to Earth-2, allowing Zoom and many other dangerous metahumans to travel to Earth-1.
Flashpoint
Creating Flashpoint is probably the worst thing Barry Allen ever did. It started with his impulsive decision to rescue his mother from the Reverse-Flash. Barry saved Nora Allen at the expense of Earth-1's reality. He eventually tried to set things right, but he created an endless amount of fractures to the timeline in the process.
In fixing the problem he created, he also had to let the Reverse-Flash murder his mother again. Everyone's lives were altered because of the decision he made and Flashpoint continued to have repercussions for seasons to come.
He Wouldn't Save Cisco's Brother
Cisco's brother died as a consequence of Barry's actions in Flashpoint, which were ironically made to save the life of one of Barry's own family . When Barry refused to save Dante Ramon, Cisco called him out for his hypocrisy and a rift was created between the two friends for a significant part of season 3.
It seemed like Barry had learned his lesson about time travel after Flashpoint, but unfortunately, it was at Cisco's expense. Overall, not changing the timeline further was a difficult, but necessary decision for the hero to make. Whether it was the heroic call or not, though, it definitely made Barry a villain in Cisco's eyes.
Savitar
Season 3's villain was literally a different version of Barry Allen. Another repercussion of Flashpoint, one of Barry's time remnants planned to murder Iris and become a speed god after claiming Barry and Team Flash rejected his existence.
Savitar, while technically not being Barry Allen, proved that Barry was capable of immense darkness and evil. Savitar ultimately failed to kill Iris and destroy Barry, but he did manipulate Julian Albert, trap Wally West in the Speed Force, and murder H.R. Wells.
Barry Stole A.R.G.U.S. Tech
In an attempt to save Iris's life from Savitar, Barry and Team Flash discovered that A.R.G.U.S. had an essential piece of alien technology that they needed to build a speed trap. Lyla made the decision not to give Barry the incredibly dangerous power source as she wasn't sure if he could be trusted after Flashpoint.
Barry immediately proved that Lyla was right to doubt him by breaking into A.R.G.U.S. to steal the tech. In addition, he further risked the timeline, ignoring what he had learned about consequences, by removing Captain Cold from a mission with the Legends in order to help him pull off the heist.
He Let Oliver Torture People
The Flash and the Arrow seem like an odd superhero pairing when you consider their vastly different approaches to fighting criminals. Oliver always favored more brutal tactics than Barry, which Barry's team certainly did not approve of during their first superhero team-up. Barry himself would never purposefully hurt criminals, but he was surprisingly okay with other people doing it for him.
Oliver provided Barry with helpful information by shooting someone with an arrow and, when Joe confronted him about it, Barry defended Oliver's methods by saying, "[He] gets results." Oliver even pointed out to Felicity that if Barry really thought about it, he would realize that he didn't want the kind of help Oliver could offer, but Barry was well aware of how Oliver operated when he suggested they team up together.
Returning Nora To The Future
After he learned his daughter was working with the Reverse-Flash, Barry locked Nora in the pipeline cells until the team could figure out how to handle her "betrayal." Unfortunately, Barry never seriously stopped to consider that he, too, had been fooled by Eobard Thawne. His worst enemy had been his mentor for months, so he better than anyone should've understood the way the Reverse-Flash manipulated people.
Barry also wasn't present in Nora's life to teach her how to be a speedster, so it was understandable that she would seek guidance from somewhere else. Even after hearing his daughter out, he decided not to give her a second chance. He left her in the future, without consulting Iris or giving her a chance to say goodbye, and warned her not to come back.