After assembling Earth’s Mightiest Heroes in Phase One, the Marvel Cinematic Universe continued the Avengers’ adventures throughout Phase Two. The world got a lot bigger, too, as characters like Ant-Man and the Guardians of the Galaxy were introduced to the roster. Following Tony Stark’s trip through a wormhole in The Avengers, the cosmic side of the MCU was expanded. With all these new heroes inevitably came new villains.

RELATED: MCU: 10 Best Unused Ideas From Phase 2

Phase Two is when the MCU started fielding criticisms of a “villain problem,” claiming that the rounded, fleshed-out heroes are not complemented by rounded, flesh-out antagonists. Still, Phase Two had a couple of pretty great villains amid the generic, forgettable ones.

Trevor Slattery

Trevor Slattery holding his hands up

Boy, this one really felt like a slap in the face. The Mandarin is Tony Stark’s arch-nemesis in the comics — the Joker to his Batman — and the marketing for Iron Man 3 really got fans jazzed up for Ben Kingsley’s take on the iconic character.

And then, he was revealed to be a beer-swilling soccer hooligan who was simply hired by Aldrich Killian to portray the Mandarin. What a disappointment. Fortunately, Tony Leung’s casting as the real Mandarin in the Shang-Chi movie looks to fix that.

Malekith

Thor: The Dark World is often called the MCU’s worst movie, so it’s unsurprising that its antagonist Malekith exemplifies the worst kind of MCU villain: a one-note character with a vague evil plan who speaks exclusively in neat, trailer-friendly soundbites.

Christopher Eccleston was massively wasted in the role, and has even spoken out against the movie in the years since it was released.

Aldrich Killian

Guy Pearce as Killian with the Extremis virus in Iron Man 3

Shane Black originally wanted to make Rebecca Hall’s character the main villain of Iron Man 3, but then-Marvel chief Ike Perlmutter nixed the idea, forcing Black to make Aldrich Killian the villain.

RELATED: Iron Man 3: 5 Reasons The Fan Controversies Were Justified (And 5 Why It's Underrated)

These enforced rewrites led to major plot holes, as it’s clear that the first act is setting up Hall as the villain, and on top of that, Killian never feels like he poses a single ounce of a threat.

Yellowjacket

Yellowjacket prepares to attack in Ant-Man

Ruthless business types are one of the MCU’s favorite stock villains. A prime example of this is Ant-Man's Darren Cross, the smarmy businessman who squeezed Hank Pym out of his company and wants to weaponize his shrinking tech.

Cross serves only to set up Ant-Man as a heist movie, as Pym recruits Scott Lang to steal the tech. Corey Stoll is wasted in the antagonist role.

Thanos

Thanos sitting on his throne in Guardians of the Galaxy

Thanos would go on to become one of the MCU’s best villains — possibly the very best — when he took center stage in the third and fourth Avengers movies in Phase Three.

However, in his brief appearances in Guardians of the Galaxy, which only served to establish his role for those later movies, he exemplified a major problem with the MCU’s model: setting up future installments at the expensive of individual films.

Crossbones

Frank Grillo in the elevator scene in Captain America The Winter Soldier

Frank Grillo may have been a little short-changed by the Captain America solo trilogy, as he’s set up as Crossbones in The Winter Soldier and then blown up in the opening scene of Civil War, but he had some great scenes in the former movie.

From the elevator fight with Cap to his third-act fight with the Falcon, the S.H.I.E.L.D. operative who knew he was working for Hydra all along appeared in some terrific action scenes.

Ronan

In Guardians of the Galaxy, Ronan is an all-powerful warlord who wants to acquire the Power Stone to destroy Xandar, which Thanos ended up doing a couple of movies later anyway. Ronan’s scenes are actually pretty boring. When he’s on-screen, the audience is just waiting for the Guardians to come back.

At the very least, Ronan’s seriousness and self-importance contrasts hilariously with Peter Quill’s brazen mockery. Lee Pace’s reaction when Quill proposes a dance-off is priceless.

Ultron

Ultron is too big for his own good. He threatens to wipe out humanity to save Earth from its own inhabitants. That plan is far too grand to cover in a single movie. Plus, it’s impossible for a character with the immense, global power of Ultron to be relatable.

RELATED: Avengers: Age Of Ultron: 5 Things It Got Right (& 5 It Got Wrong)

James Spader managed to salvage the character a little with his creepy vocal performance. He made Ultron’s scenes entertaining, even if the movie as a whole doesn’t really hold up.

Alexander Pierce

Alexander Pierce at the SHIELD building in Captain America The Winter Soldier

The Russo brothers’ direction of Captain America: The Winter Soldier was heavily influenced by the paranoid political thrillers of the ‘70s. In the post-Watergate era, movies about government conspiracies were rampant, and the hero at the center of it all was usually played by Robert Redford.

So it was a stroke of casting genius to hire Redford to play the S.H.I.E.L.D. bureaucrat responsible for The Winter Soldier’s shocking conspiracy that Hydra’s been running things for 70 years.

Nebula

Nebula

Although they eventually became allies in the sequel, Nebula was an enemy of Gamora’s in the first Guardians of the Galaxy movie. She was determined to kill Gamora, just to prove to their adoptive father Thanos that she could.

Under the thumb of both Thanos and Ronan, Nebula became blinded by that desire. When she thought she’d actually done it, after blowing her sister out into space, her remorse was palpable.

The Winter Soldier

bucky barnes

The best villains are the ones who are close to the hero. Luke Skywalker is Darth Vader’s son; T’Challa is Killmonger’s cousin; in Sam Raimi’s Spider-Man trilogy, all the villains happened to have a close personal connection to Peter Parker.

In Captain America: The Winter Soldier, Steve Rogers has to wrap his head around the fact that the brainwashed assassin who’s trying to kill him is his childhood best friend whom he thought he saw die almost a century earlier. It added a real emotional layer to the action.

NEXT: Star Wars: Ranking All The Villains In The Prequel Trilogy