Which crypto has no network fee?

Could you please elaborate on which cryptocurrency does not have a network fee? I'm intrigued to learn about any digital asset that manages to operate without incurring any transactional costs, as this is a unique feature in the cryptocurrency space where network fees are often a necessary component to maintain the security and decentralization of the blockchain. Are there any specific characteristics or design elements that enable this cryptocurrency to operate without a network fee? Furthermore, what are the potential implications of a cryptocurrency without network fees on its scalability, decentralization, and overall adoption?