I would've never thought that this hotel is so bad. It has all its goods in the window but no good inside. 听起来自然吗？

This will sound more natural:
"I would've never thought that this hotel was so bad. It has all its goods in the window, but none inside."

When you use past tense in your sentence, be sure to use it throughout. ^^

"I don't think this hotel is so bad." <--- present tense
"I would have never thought this hotel was so bad" <--- past tense
:)