I just encountered this phrase in this video:
全然いいとおもいます。
As far as I know 全然 is usually used with negatives but can be used in positives, too, in colloquial speech. However, this got me thinking: what would be a "more grammatically correct way" to say the same?
"別にいい” also seems colloquial (the man at around 4:20 in the video uses it)
Apart from that, I can think of "結構です”, but it seems to vague; it makes me feel more like I am in a shop or restaurant saying I do not need anything else...
完璧 also seems out of place in this context. It would mean literally "perfect", like attributing a degree to it (good, better, perfect)...
The only other one I found that seems possible to me is 完全に, like "完全にいい", and I found some examples of what seems native speech via Google (「完全にいいぞ. 」「完全にいい1日となりました。」). Seems neutral
However, that's about it. Are there any obvious alternatives that I'm missing?
P.S. What's interesting, the next person used essentially the same construct, "全然いいと思う”, just another level of politeness