You’ve got some nice stuff happening in this painting.
The few things I think could be better are:
-The figure’s silhouette can be a lot more clear and effective. It’s a bit vague right now. Tweak the forms and really make him distinct.
-The creature’s pushed up a bit too close to the top border. If this scene is meant to be epic, then give it a bit more breathing room.
-In some areas, such as on the back of the creature’s hand, I’m seeing lighting information that doesn’t really match the rest of the scene. Think carefully about where you are placing your highlights and how they relate to the position of your main light source.
-The overall lighting scheme is a bit confused. If that bright spot in the sky is your main light source, then you need to have the creature cast a shadow–a big one that goes over the crashing waves and the figure. It’ll actually increase the tension and make the scene even more scary.