I play mtg, I read the novels (Artifact Cycle, Rath Cycle, Invasion Cycle, Oddysey Cycle and the first book of Onslaught Cycle) plus their wikis, may I ask if this is a Pre-Mending or Post Mending Bolas? Anyway, based from my knowledge of the lore, Nicol Bolas is known for being a ruthless and cunning. Take note if this is a Pre-Mending Bolas then it is trouble, meaning he is an old walker. Old Walkers are near omnipotent, can travel or "walked" the multiverse in the blink of an eye, has an ability to destroy artificial planes, devastate a natural plane and had unlimited number of spells.
When we say unlimited number spells, you need to take it literally, because the old planeswalkers can be indestructible, can delete an opponent, can manipulate forces of nature, can be intangible and etc... You know, a living infinity gems/stones, because they became Magic or the essence of the 5 mana(RBWGU) itself.
But, they also had an achilles heel, if the opponent managed to destroy or consume their essence or managed to corrupt or trap the Planeswalker then its over for the Planeswalker, but this is a feat that takes wits. And the likes of Nicol Bolas who is very manipulative and had the ability to mind control and bend realities, his opponent needs to outwit him. Take note, in one of the novels (Legends Cycle), Tetsuo Umezawa (descendant of Toshiro Umezawa of Kamigawa Plane), a plain mortal who is as strong as Kenshin Himura or Mitsurugi from Soul Calibur, managed to trap him by tricking him to get inside the Meditation Plane and shattering the temple that contains the host body that Nicol Bolas stayed(How Nicol Bolas have a host body? You need to read the Ice Age and Alliance Cycle for that and its Urza's fault why Planeswalkers cannot go walked physically to Dominaria and Bolas needs a Madaran host). Sadly, his essence wasn't destroyed so he managed to return to Dominaria and obtain again his physical form after thousands of years and resumes his schemes against the good guys(Time Spiral cycle).
Did I forget to mention that he still had that unmatched intellect?
So for Cronus or any hero who will face this Elder Dragon needs to win a battle of wits and its not just a fist fight or any hax sh*t or anything that even it involes a multiple spiral big bang. IT IS A BATTLE OF WITS. Act impulsively against an Old Planeswalker, like Bolas or Urza, is a suicide even if you're Queen Serenity, Zeno, Cronus, Galactus or Thanos that wields the infinity gauntlet with all the gems in it.
The same concept is applied on his post mending state, the difference is Cronus has a stronger chance of winning, but then again he need to outsmart the Elder Dragon who managed to outwit and pacified some gods in his lore