Using -no-sandbox worked for me!!
I was experiencing this slow loading page issue (even About Opera page, 6-7 sec) since last v25 patch arrived.
I was about to uninstall Opera 25 after all these years! Even this page was loading loading in 9-10 sec. (in first opening of any page)
Now I used -no-sandbox on the link and now It's fast again.
I don't think it's an ideal solution. So, note it.