Fiora can solo top against most strong bruisers that solo and come out on top. She has very strong damage at lvl 4/5. Never directly fight a champion only attack in short bursts until u have the advantage. Do not get over confident and turret dive with your ult you may not live or get kill its not worth it. One of the common solo top you can fight against as her is Mordekaiser/Nasus/Volibear/Talon thanks to her W she can parry at least one of their abilities.