Proton Unlimited could refer to a premium offering by Proton, which is known for its privacy-focused services like ProtonMail for secure email communication, and ProtonVPN for secure and private internet browsing. If Proton Unlimited is a subscription tier, it might provide enhanced features such as higher storage limits, advanced security measures, faster connection speeds, or the ability to connect more devices simultaneously. However, specific details about 'Proton Unlimited' are not clearly established in available resources.