The Waterfall model is a classic linear methodology that emphasises organised planning and documentation through a step-by-step progression through discrete phases. Although it offers a great deal of documentation and predictability, its rigid structure may make it more difficult to adjust to changing requirements. On the other hand, the Agile methodology supports customer-centric and iterative approaches, enabling flexibility, ongoing input, and incremental delivery. On the other hand, DevOps is an example of a technical and cultural partnership that combines operations (Ops) with development (Dev) to accomplish automation, deployment, and continuous integration. In this paper, we compare these three. The characteristics and trade-offs of each technique are carefully examined in this comparative analysis with regard to flexibility, adaptability, customer collaboration, delivery speed, documentation emphasis, continuous improvement, culture, and automation.