1. The T-1000 and Odo are transported by Q to Gothos to battle. No prep. Can either take down the other? (Trelane is present but doesn't interfere.) 2. Who would make a better spy? 3. Has Odo ever been shown to be affected by the environment in any way (such as Kirk being choked by the toxic air in "The Squire of Gothos")? Is there any hypothetical environment (real or imagined) which would affect Odo or the T-1000 (perhaps the Demon Planet from Voyager)?
1. I don't think either of them would engage in a straight fight because what would the point be really? If the T-1000 wanted to kill Odo he'd find a way. If he gets his hand on a phaser Odo's really done. 2. On modern day Earth they would come up even. In Star Trek's future probably Odo. The T-1000 is made of liquid metal. Surely the advanced sensors of the 24th Century would detect the T-1000 in a nanosecond. 3. They're both made of liquid. I imagine an ice planet or a lava planet would fuck them up pretty royally.
Odo's shapeshifting abilities are more advanced than the T-1000's, so I give him the edge. It's pretty difficult to fight against someone that can turn into a non-tangible form like fire or mist. One problem that Odo would face is if the battle rages on for a long time. T-1000 could just wait him out and force Odo to make himself vulnerable while recharging if he had to.
The mirror universe Odo seemed to take full damage from a disruptor and was killed. I can see an energy weapon's beam going through the T-1000. The hole would be slagged/melted into a cylinder of regular metal that the T-1000 would have to rid itself of, so multiple hits would reduce its mass. Odo, being organic, dies from hydrostatic shock--which is no myth: http://en.wikipedia.org/wiki/Hydrostatic_shock On the same note (you will forgive the thread hijacking of course) I think a more interesting question is this: Carpenter's Thing vs The Blob The Thing (I assume) is a very advanced creature, with DNA even more complex than Species 8472. It wants to build organic matter up. The Blob is very primative, has entropy on its side, and wants to break everything down. The Thing, on the other hand, may see the Blob as simply a rich petri dish full of culture/nutrients. Who absorbs whom?