I get why they couldn't have Odo transforming into a bear all the time, but this would mainly just be another actor, and I'd say his potential feels a bit wasted.

When he gives you that stare, the one where he crosses his arms and turns his body slightly to the side, eyes glaring deep into the depths of your being, it is then you've seen Odo's battle form.

Odo used harumph. It’s super effective!

I have a feeling if he had always turned into a Tarkasian bear for battle, fans would have complained that he is too much like the Hulk.

I think they landed on this idea and the sufficiently large budget for the CGI too late but the tentacle throwing golden blob is an interesting battle form.

Isn't it funny how the production technology informs the storytelling? I heard that TNG in the first two seasons had a price tag of something like 5000 dollars per hand phaser beam so they used almost none. In S7 they shoot 100 times willy nilly in Gambit and hit almost nothing, no problem. Odo in S1 morphs in the pilot and then almost never on screen for a long time. And by S6 or 7 they're like, sure, morph him into fire, fog, or an emu, wgaf!

It's very interesting, and although frustrating at the time I wonder if in retrospect it was for the best. Without being able to fall back on effects as a crutch you have to make sure the show stands up on the story and actors alone, and that can only make those things better.

Transporters were originally used because shuttles were expensive to film.

Imagine the Klingon boarding scene in s4e2, if he just doubled in size and smashed through the Klingons

Odo SMASH!

It's the same reason the T-1000 didn't need to transform into "attack mode". Odo is a particularly deadly type of fictional character that could kill another fictional character in thousands of different ways in a few fictional seconds.

Besides, Humanoids are the most deadly type of fictional character. Odo IS cosplaying as the scariest thing in the Universe, every single day.

is tripwire Odo not deadly enough for you?

Odo was a lover, not a fighter. Just check out those bedroom eyes!

I could see him doing that to scare off someone/something, but not for actual battle.

If you could change into anything, including tentacle goo, then just making yourself big isn't going to help much. Might as well just turn into a living straight-jacket and constrict as needed to subdue the baddie.

His battle form is Stretch Armstrong