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.  

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.