Tyrant's base power level is not on the same level as Galactus. Through the traits given to him by Galactus, Tyrant can attain levels of power approaching Galactus, but they do not originate in Tyrant. As a matter of fact, Tyrant's threat level us entirely dependant on the amount of energy he has stolen from others.
Tyrant can b cut-off from external power sources. This can result in his power diminishing to a point near high-herald level.
Classic Mangog's power originated from him. From the billion billion godlike beings within him. (His ability to draw power frim other emotional sources were only recognized later). The only way he could b defeated was through Odin's ability to reverse/unmake that which he made. Period.
Regardless of attempts to debunk the wording in Mangog's initial appearances, he was described as a threat level well above Odin. Throughout the stories, we constant got reminded of this fact by Odin and Mangog himself.
Unless somebody can find sources explaining how all of this was put in a book as a deception, or a panel where Odin says, "i was only foolin around. Mangog is no big deal". We will stick with the wording of the stories, as ee do for all the other similar character situations in this forum. He is what the books say he is.
Thanos easily weathered a full assault from Tyrant. From Odin, not so much. Odin is well above Tyrant's normal power level. And, no, the SINGLE POWER SPHERE, of ONE SINGLE BEING that Thanos was holding, not even knowing what it was, did not hold off Tyrant's attack. If it did, Tyrant is obviously too stupid to utilize the thousands of spheres he was hoarding.
Tyrant's history is actually similar to Mangog with a few differences that lean in Mangog's favor.
Both r surrounded by stories and descriptions from a distant past that never appeared in a book. Those stories and descriptions create a profile with instant "battle-cred".
Those unseen stories describe both characters as threats to incredibly powerful characters.
The difference is, Mangog actually shows up and Odin starts crapping, explaining, hiding and getting beaten up. (And, basically, has never been seen doing that stuff in a book again).
Again, Tyrant, not so much.
Tyrant basically spent his appearances creeping around, stealing power from other characters, so he could get more powerful. With each character escape, Tyrant became much more of a little sissy-child, leaving many of us feeling bad for him and how his daddy treated him. (Sorry, i just couldnt hold that stuff in any longer.)
There's plenty more if anybody would like seconds.
He's freakin weak. Weak ass energy vampire, kidknapper, chewin his shirt. Original Mangog would simply tear Tyrant apart, shrugging off his pansy-beam attacks until there were no more. Maybe from time to time, transmuting part of Tyrant's physical makeup into spagetti, or encasing him, or parts of him in varying forms of solid matter.
Or, he might just want to physically tear Tyrant apart from his head to the end of his extension cord corn-rows.
One thing is for sure, Mangog is not going to b interested in listening to Tyrant throwing a fit because Galactus wouldn't let him breastfeed! Or trying to intimidate Mangog with stories of how powerful he got to b once upon a time. He will tell Tyrant to man-up, then begin the show.