Odo vs Reed Richards
Why are we here?
"Superboy Prime (the yelling guy if he needs clarification)..." - Postmania
"...dropping an orca whale made of fire on your enemies is a pretty strong opening move." - Nik
"Why throw punches when you can be making everyone around you sterile mutant corpses?" - Pendaran, regarding Dr. Fate
Not even a contest. Reed wins easily. Vastly greater stretching powers. Far greater hitting power and durability.
If it was a contest of shapeshifting to look like a specific person, Odo's species (not Odo himself) would win.
Power with Girl is better.
Odo can shape shift into fire, but I would bet on Reed's outfit being insulated against whatever Odo's best output is.
That said, Odo probably has a phaser as his regular gear, so he might be able to wide-angle blast Reed's head before getting disarmed.
You'd think, but no, IIRC, Odo specifically eschewed the use of firearms, preferring to rely upon his powers in his capacity as Security Chief. So unless I'm misremembering, no phaser as standard equipment.
Strange to think that an ordinary red shirt with a type-1 phaser might do better against Reed than Odo....
by the end of the series, odo had learned how to turn into fire and gas.
not even sure if reed can even hurt him.