I think there's an instance in Ghosts of Onyx were a bunch of Sentinels get together and pull off a fireworks show which some UNSC types think would have been done by their nuclear artillery, but I've not read the novel.
Our knowledge of what the Forerunners were capble of is limited we have only minimal knowledge of their technological capabilities. A portal opens connecting the twoĪlmost totally impossible to fathom. This is long before the events of Halo by the way. By fiat, the Flood disappears and the Forerunners decide to take over the SW galaxy. 2) Palpatine has crushed the rebels at Endor.
