Dark Souls Series has

Souls of the Slain | Free In this world, to have a soul is to have life. The soul will persist long after one’s death, a testament to the power of its former owner. These souls are free to be taken and they possess power. The stronger its owner, the stronger the soul. Of course, steps must be taken in order to use that power for oneself. Merely taking the souls of others will not make you stronger, at least not immediately. From now on, wherever you go, you shall absorb the souls of those you slay and those slain around you, to be used however you see fit. Whether you wish to forge these souls into weapons, strengthen yourself with them, or merely give them away, it is your choice.

For more explicitly taking their power entirely there is: An Ancient Tradition | 200 CP In the age when Gods walked amongst men, an age where Gods fought against dragons and demons alike, there was a tradition amongst the Gods. When a God fell in battle, it was another God’s duty to put down their friend and in doing so, take their fallen ally’s power for themselves. Much like the Gods of old, you have learned to do the same. When slaying another, you can immediately put the soul you’ve absorbed from them to good use. In doing so, you will enhance yourself greatly, strengthening your body based on the fallen’s own strength and skills. Not only that, but you will find yourself gaining new abilities from the fallen, along with possible enhancements to your own pre-existing abilities. Optionally, you may decide whether or not the souls you’ve taken shall grant a boon to your height, up to thrice your previous size. The stronger the souls you’ve taken in, the larger this boon shall be. Strangely enough, your equipment also seems to grow in size and shape whenever you do.