Thanos
He is stronger than the Hulk. He is more like Genghis Khan. He is a force of nature. He has a spiritual wisdom well beyond all the other characters. He is a conqueror of worlds. He does not have a weakness, and that is what makes him so threatening.
http://boundingintocomics.com/2018/03/21/avengers-infinity-war-director-reveals-the-strength-of-thanos/
Here you see the early establishment of just how fearsome Thanos is even without, he has got one stone here and I do not think he is even using it, McFeely said.
He is not using it, Russo said. This is to show that Thanos, the Genghis Khan of the Marvel Universe, he is unbeatable in 1-on-1 battle. He has conquered thousands of worlds. He is a much more polished fighter than the Hulk, and Thor, and Loki.
https://youtu.be/PbWzC6pgEYc
^ Clip showing Thanos defeat the Hulk and dismissing Thor casually after both heroes cheapshot him to begin the exchanges.
From the films opening scene he already has the Power Stone, and by the time the opening title plays he obtains the Time Stone as well. But wielding two Infinity Stones does not make him the most powerful villain in the Marvel Cinematic Universe. He already had that distinction before his hunt for the stones because of his strong will.
The creative team from the movie previously elaborated on Thanos strength, revealing that he did not need nor did he even use the Infinity Stones to defeat the Hulk. Instead he handily beat him at his own game, with brute strength, in the films opening scene.
https://comicbook.com/marvel/2018/08/03/avengers-infinity-war-thanos-powerful-without-infinity-stones/
Relevance-Thanos brings a determination unrivaled in the MCU to the goals he sets before himself. He has the experience of conquering countless worlds so Asgard is just another target. He also possesses a spiritual wisdom above everyone else in the MCU. His skills in combat formidability are beyond those of Thor who is arguably Asgards greatest warrior as per the filmmakers. More evidenced by his feats in Infinity War which shows he can parry attacks while fighting multiple foes simultaneously with a wide assortment of different powers and abilities. A few gifs demonstrating his fighting prowess.
https://youtu.be/rivbQcxzmpk
^ Clip showing Thanos battle seven opponents by surprise on Titan such as Iron Man, Dr. Strange, Spider-Man, Starlord, Drax, Mantis, and Nebula.
Thanos forces
A) Black Order
Thanos most devoted and super powered loyalists. Each member brings a different skill set or strength to this formidable group all determined to carry out the agenda of Thanos. Each member here are the stepchildren of Thanos who are fanatical in service from previously conquered planets.
Thanos elite warriors
1a). The Maw
Referred to as a techno mage on the audio commentary of Infinity War this gif shows the level of control/precision he has over his molecular telekinetic powers.
Relevance-His abilities are quick, precise and extremely effective in combat. He has the experience of conquering worlds under Thanos and the obedience to carry out Thanos agenda without question.
https://youtu.be/JMghAghNYx8
^ Clip showing off Maw and Obsidians fighting prowess.
1b). Cull Obsidian
The Hulk like brute of the Black Order. Super strength, extremely durable, skilled with his weaponry.
Relevance-An enforcer with the strength to overpower Hulk buster armor and get the drop on Iron Man in an extended fight with help from Spider-Man.
https://youtu.be/odiZ-e_2VCU
^ Clip showing Cull Obsidian vs. the Hulkbuster armor.
1c). Proxima Midnight
What makes her different than Obsidian is her agility and elusive combative skills. She has mastered her weapon the spear. She can emit force blasts from her weapon. Able to handle the likes Black Widow and Okoye too highly trained and skilled foes simultaneously just fine.
Relevance-Battle awareness during combat scenarios. She is objective driven. She knew the moment Scarlet Witch was on the field to know Vision was unguarded to deploy Corvus into attack.
https://youtu.be/oun-sgQbssQ
^ Clip showing Proxima Midnight get the drop on Scarlet Witch and having the skill to handle Black Widow and Okoye simultaneously.
1d). Corvus Glaive
Another highly skilled and ruthless combatant who works well with Proxima in battle. His main weapon the Glaive was able to damage Vision whose body consists of vibranium, preventing him from phasing for the duration of the film, and able to block the mind stone blast from an Infinity Stone. One on one he got the better of Captain America so his hand to hand skill and strength are exceptional.
Relevance-His skillset and weaponry is capable of damaging Vibranium so this means any higher end durable foes are fair game.
https://youtu.be/nPH_yHau9Xw
^ Clip showing Corvus Glaive injure Vision and then fight him. He shows mid clip he can deflect the mind stone power with his Glaive weapon.