The Silver Surfer is Norrin Radd who was an astronomer on the planet Zenn-La. Norrin was just living a quiet life until Galactus came to feed off of his planet. To save his love, Shalla-Bal, Norrin agreed to become a Herald of Galactus. Basically his job is to roam around the universe and find planets for Galactus to eat. To aid him in the task, Galactus gives him the Power Cosmic. The Power Cosmic is just a portion of Galactus' strength, but even a portion is still a HUGE amount power.
The Silver Surfer is coated all in silver and also has his board which he can control with his mind. The Surfer has a wide variety of powers. The Power Cosmic gives him super strength, speed, and durability. With his board he can fly extremely fast, to the point of crossing light years in mere seconds. With the Power Cosmic he can also manipulate matter. He can completely change objects and even accelerate life and cause things to evolve. There is basically nothing that he can't do.
As a Herald of Galactus, Silver Surfer has often taken the role of a villain, but it's shown that he has a good heart and is a good person. He's had to take on some of the most powerful characters in the Marvel Universe both good and bad, and usually wipes the floor with them.
10 Hulk
Silver Surfer has handily defeated the Hulk multiple times. While the Hulk is incredibly strong and one of Marvel's most powerful heroes, it's how the Silver Surfer was able to take him down that shows just how strong the herald of Galactus is. Silver Surfer didn't just beat the Hulk down, one time he used the power cosmic to drain Hulk of all the Gamma Radiation in his body. The Silver Surfer was literally able to turn the Hulk back into Bruce Banner in mere seconds.
9 Cable
While the time traveling mutant is already one of Marvel's most powerful heroes, when he isn't held back by the techno-organic virus he is nearly unstoppable. Cable with full use of his powers is almost on the level of a god. When he does reach this power level, Silver Surfer decides to bring him down. Though the fight drags on a for a little bit of time, it's clear that Silver Surfer is just playing with him. At the end of the fight Silver Surfer completely annihilated Cable even at full power.
8 Mephisto
Mephisto is a villain in the Marvel universe clearly modeled after the devil. He is an immortal demon and is extremely powerful. The character is one of the main foes for the Silver Surfer and they have faced off several times. The Silver Surfer was able to best him in his own dimension, clearly showing himself to be more powerful.
7 Wonder Man
Wonder Man is a sometimes hero and sometimes villain. He was imbued with "ionic energy" by Baron Zemo to try and match the Avengers, but it turned out much more powerful than expected. Wonder Man has super strength and a host of other powers from his ionic energy. Notably he has faced off against the Red Hulk and come out on top, so he is definitely a powerhouse. Even with all that behind him, he was no match for the Silver Surfer.
6 Ronan
While we got to see some of his power in the MCU, Ronan the Accuser is a serious force in the comics. The Silver Surfer shows his strength by easily subduing him. Ronan learns his lesson and powers himself up further before trying again, but it still isn't even a close contest. Silver Surfer is able to dominate Ronan without much difficulty.
5 Beta Ray Bill
While the only glimpse of Beta Ray Bill that we've seen in the MCU was a brief cameo in Thor: Ragnarok, the character is a fan favorite. Beta Ray Bill is a horse looking alien that wields the power of Thor. That means that he is about on the same power level as the god of thunder himself. Silver Surfer doesn't find him to be much of a match and actually apologizes for the beatdown while he is giving it.
4 Firelord
Firelord is another Herald of Galactus, and if you haven't guessed by now, he controls fire. While the Heralds of Galactus have differing power levels, one thing is for sure; they are all insanely powerful. Despite this, Silver Surfer is able to take Firelord down pretty handily. The blasts of flame don't even seem to faze him too much.
3 Nova
Richard Rider was a member of the Nova Corps and after the rest of the corps was wiped out he gained sole possession of the entire power of the Nova Force. Rider is shown in the comics to be incredibly strong, but ultimately stands no chance against the Silver Surfer. What Nova didn't know was that the Silver Surfer was trying to protect him from Galactus.
2 Ravenous
Ravenous was part of the Annihilation Wave as the leader of the Seekers. Coming from the Negative Zone, Ravenous uses the "Essence" which he says is the Negative Zone's version of the Power Cosmic. In a lot of ways this makes Ravenous the counterpart to the Silver Surfer, but when it came down to a fight, the Surfer showed himself to be superior. With a huge blast the Surfer is able to knock out Ravenous and escape from the rest of the wave.
1 Morg
Morg is another of the Heralds of Galactus that got a bit too power hungry. Morg was intent on taking over, and was easily able to defeat other Heralds. Silver Surfer enlisted help to take him down and their fight was legendary. When the Silver Surfer and Morg eventually clash, the battle levels an entire planet. In the end Silver Surfer walks away unharmed.