The Call Back to it in War of Kings, where Nova negotiates with Blastarr and reminds him what he did to Annihilus. And that he can easily do it to him.
The first issue of vol 4, where Richard kills a massive Kaijuu that's been rampaging around a planet for several months, mainly to stop the people who let it from trying to use it again.
During the tie-in to Annihilation: Conquest, Richard becomes the only being we ever see who manages to fight off the Phalanx infection, and then he and the Worldmind manage to escape from the impenetrable barrier the Phalanx had set up.
During the Secret Invasion tie-in, the Worldmind managing to activate a legion of Death's Heads robots and sic them on the invading Skrulls.
Richard and the new Nova Corp recruits versus the Serpent Society. The entire fight lasts a grand total of one point eight seconds.
Richard gets depowered. Normally you'd expect several issues before he gets his powers back, but no, Richard manages to go and get him some replacement powers in the form of the Quantum Bands, hunts down Worldmind, kicks its ass and gets his powers back, saving the thousands of beings that had been abducted in the process.
Robert managing to hold down Strontian for several hours. Strontain happens to be the same species as Gladiator, and has already been portrayed as completely unstoppable. Later on Richard admits that even with the entire Nova Force at his command he wouldn't have been able to do that. Score one for the nerdy little brother.
Nova vs Sphinx in Realm Of Kings, when Nova defeats the god with the power of SCIENCE!