While Surat-un-Nasr shows which of the two parties presented in Surat-ul-Kaafiruun will be successful, this surah focuses on the destruction of two of the prophet's worst enemies among the disbelievers (Abu Lahab and his wife), thus reassuring the prophet of the upcoming victory announced in the previous surah.
Abu Lahab was an uncle of the prophet. This teaches us that the ties of faith are stronger and have priority over the ties of blood.
This surah is one of the miracles of the Qur'an. By condemning the two (Abu Lahab and his wife) to hell, the surah is making an indirect statement that they are not destined to accept Islam. They could have easily discredited the Qur'an by simply saying "laa ilaaha illallah" even without sincerity, but they never did even though they had every opportunity to do so.