Photoinduced enhancement of hydricity of palladium hydride species enables unprecedented hydride addition-like ("hydridic") hydropalladation of electron-deficient alkenes, which allows for chemoselective head-to-tail cross-hydroalkenylation of electron-deficient and electron-rich alkenes. This mild and general protocol works with a wide range of densely functionalized and complex alkenes. Notably, this approach also allows for highly challenging cross-dimerization of electronically diverse vinyl arenes and heteroarenes.