Corrosion in complex acid environments, such as high temperatures and acidic downhole conditions, remains a critical threat to well integrity during oil and gas acidizing. This review firstly examines the influence of downhole variables, including temperature, acidity, and steel, on the performance of organic inhibitors. It analyzes molecular design strategies that enhance the stability and adsorption of traditional inhibitor classes, including Mannich Bases, quaternary ammonium salts, and benzimidazoles, through structural modifications such as rigid heterocycles, extended alkyl chains, and multi-dentate architectures. The discussion extends to synergistic formulations, sustainable alternatives derived from biopolymers or green chemistry, and intelligent responsive systems. Furthermore, the growing role of computational methods, from molecular dynamics simulations to AI-driven molecular design, in accelerating the discovery of high-performance inhibitors is highlighted. Together, these advances offer a comprehensive and forward-looking perspective on developing adaptive, efficient, and environmentally compatible corrosion protection strategies for next-generation hydrocarbon extraction.