Minato Namikaze, aka the Yellow Flash, is one of the most idealized characters in the Naruto world, but very little known about the famed legendary 4th Hokage. So let us breakdown what we actually do know.
First lets start with his abilities. Known as the Yellow Flash, Minato was fearede for his incredible speed. In fact he was said to be so fast that even the Raikage (the fastest of the current Kage) said that there would be no one who could surpass him. It was Minato incredible ability to use the Flying Thunder God Technique that gained him this fame. He was so good at it that even the inventor of the ability, the famed 2nd Hokage, Toribama, remarked that Minato had surpassed him.
Minato's other claim to fame was his invention of the Rasengan. After years studying the Tailed Beast Ball, Minato was able to mold his chakra into a powerful ball of chakra. As Naruto found out, this technique proved extremely difficult to learn and to control. It was a technique that Jiraiya said completely dwarfed the power of the Chidori, Kakashi's famed attack.
His powers were so famed that years later if ill will befell Konoha, many villagers would be left wondering what if the Fourth Hokage had survived. He was and remains one of the legendary fallen heroes of the Leaf Village.
Beyond his physically prowess, Minato was known to be very intelligent. He was able to make sense of Obito's plan quickly enough to be able to sever the connection between Obito and the Nine Tails, save his son, and be able to save Konoha. He was also able to foresee years into the future that Naruto would need the power of the Kyubbi in order to stop Obito/Madara. While he knew he would cause years of pain for his son by making him a jinchuriki, he was wise to see how the Kyubbi would eventually be able to help Naruto.
Minato's personality was that of a loving kind father and husband who was fiercely loyal to his "family," whom he believed included no only his son and wife but all of Konoha. He was so loyal and courageous that he voluntarily ended his own life in order to be able to seal the Kyubbi away and save Konoha.
Personally, I think that Minato is the one character I would have loved to see have more action. His speed to me is just incredible. The fact that he was able to out race Obito (whom everyone including Naruto and Kakashi together) had a hard time hitting, and outclass the Raikage even when the latter was using his lighting nature to increase his speed, is just unbelievable. I am leaving some videos here to show just how amazing this Shinobi was.