"I thought this would look good" in Chinese?
Edit: I overlooked the simplified Chinese tag. Now adding simplified chinese version back

I assume your sentence have a [hidden context]:

I thought it would look good [but it turns out to be awful]



In this case I would translate it as:
我以為那會好看(Trad.)/我以为那会好看(Simp.)

To divide it word by word then reverse translate:

(我)(以為)(那)(會)(好)(看)

(I)(thought)(that)(would)(good)(look)



Google translate suggested the translation 我認為這會好看(Trad.)/我认为这会好看(Simp.)

But if I reverse translate this back to Eng I would say it is:

(我)(認為)(這)(會)(好)(看)

(I)(think)(this)(would)(good)(look)



The difference between 认为 and 以为 is not focused on tense, but in tone and assertiveness.

认为 : think, with a sense of confidence in oneself (a.k.a. belief, assert)

以为 : wrongly thinks (a.k.a. thought)