It doesn't entirely matter.
Spawn has "DIED" numerous times and he is still here now.
So technically, truly defeating Spawn is almost an impossiblity.
Here are my reasons why Spawn has such an advantage over someone like Exitar:
1) You are contrasting Spawn with Galactus.......Wanna talk about Galactus and his ability to create heralds......Spawn is connected to the LEGION...an army of nearly countless hellspawns each with there own unique power and fighting capablities.
2) Spawn as ruler of Hell would beat Exitar....in the 8th level of Hell, King Spawn is incharge of its very fabric. Exitar travelling to Spawn's domain at that point would have been futile, Exitar would have had no power there.
3) Spawn killed Malebolgia who could be comparable to Galactus.
4) Spawn SCARRED Mammon an entity definately equal to Galactus, if not superior, in terms of Hellish Authority. What Galactus is in his universe is what Mammon is in Hell, if not stronger.
5) Second Age Spawn was virtually unstoppable. He transcended the rules of Heaven, Hell, Earth, every aspect of Reality you can think of. heavenly weapons had no effect on him, Mammon's superiority made no difference in thier first showdown.
6) Spawn comprises of Necroplasm, chopping off his head doesn't kill him anymore, it only stops him temporarily. He's virtually immortal, even in the latest Spawn, before he escaped Thamuz' torture, even Mammon was shocked "I actually think the HellSpawn is truly dying this time....how is that possible?" He asked. He's one of the major devils in Hell, and even he was completely shocked.
7) Try to keep in mind, Image's version of Hell is much more extensive and greater than Marvel's. Marvel treats Hell and any intepretation of it as "pocket dimensions" "minor realms within the universe". Mephisto is a joke, so don't bother comparing him to any of the devils of Image.
In Image Hell is like an endless spectrum of torturous universes, and each "universe" or level of Hell has its ruler. Marvel doesn't treat Hell this way, which is why Galactus appears to have much more authority over any demonic force.
I'm not saying Exitar is no match for Spawn.....I just don't think Exitar can ensure Spawn's absolute submission.