Hyouken no Majutsushi ga Sekai wo Suberu

Both anime feature an overpowered main character who tries to live a normal life in high school. Both main characters' attitudes and personalities are similar as they are straightforward and do not flinch at talking with girls. They also share a similar backstory related to the military and being a soldier. Both main characters are considered to be "worse" in the eyes of other standings due to their standing/background/lineage, despite their overwhelming strength. Both anime have a more "science"-y background explanation for the magic used.  

Surprised no one has recommended these two shows yet. Seemingly normal guy who is good with girls comes to a magic school on the recommendation of a high-ranking member of the school, someone who he used to work with in the army. No one thinks much of him at first, but he's secretly a world-class mage with military experience and the strongest asset in the country's military. Some trauma occurred related to the battlefield, so he is recommended to come to the school and live a normal high school life. While there, he befriends many girls, who eventually develop strong crushes on him. While he is hesitant to reveal his power at first, he does so to protect the girls and other students. If you like one, give the other a try.  read more 

Both series blend academy life with an overpowered past hero concealing their identity while focusing on the importance of forging strong friendships. 

Both have same vibes where ML is powerful. He is popular among all FL's, but he is oblivious of their feelings. They all love him and competing against each other.  

Both anime feature an overpowered main character and a red/pink haired girl who uses fire attacks. Similar theme with battle magical highschool, main character has an Harem and the general feel is very similar. 

In both anime the main character is being looked down on due to his standing, and both have a main girl lead with red hair using fire attacks. Both anime also feel similar in the battle magical high school genre. Rakudai is more of a straightforward romance while Iceblade Sorcerer has a Harem. 

Surprised this hasn't been listed yet - it's almost like watching the same anime with a few slight differences. I will say I did preferred Kenja no Maho (was great if you love those overpowdered MCs with a good comedy twist added) but they're both fun (if ya don't take 'em too seriously). They're so similiar. MC is OP and more or less hiding his power while going to a school. Both are technically commoners but have actually crazy backgrounds of their teachers/masters and their families. Both make friends with other students and more or less share their secrets with them. Honestly, it's the same anime with minor differences. Plus they have a very similar feel in both art style and over-all vibe. So they're pretty interchangable, in my opinion. read more