The deformation energy in the fusionlike deformation path has been determined from a generalized liquid drop model taking into account both the proximity energy, the asymmetry and the microscopic corrections. Multiple-humped potential barriers appear in the exit and entrance channels of the heaviest elements. In the fission path of actinides, the second maximum corresponds to the transition from compact and creviced one-body shapes to two touching ellipsoids. A third peak appears in certain asymmetric exit channels where one fragment is almost a double magic nucleus with a quasi-spherical shape while the other one evolves from oblate to prolate shapes. The heights of the double and triple-humped fission barriers and the predicted half-lives of actinides follow the experimental results. In the fusion path leading possibly to superheavy elements, double-humped potential barriers appear for cold fusion but not for warm fusion. The $\alpha$ decay half-lives can be reproduced using the experimental $Q\alpha$ value.