If a simple, stripped down site packed with full hentai episodes is what you need, then go ahead and visit Hentai.AnimeStigma.com, also known as HentaiStigma.net, to watch both 2D and 3D hentai.
There are hundreds of series listed here and thousands of episodes in total to watch, while about 400 of them are uncensored. Although the front page on Hentai.AnimeStigma shows a lot of raw episodes without subs, don't worry because they get subtitles in a few days, or no later than two weeks. The situation is a bit different with older raw content as it's not usually subbed, but you can always report asking for subs. When streaming, you can pick between an old and new player that look almost the same and work great. Both of them have no settings to adjust streaming quality and no download options, and video quality overall is average to no more than 720p.
As you will notice, the HentaiAnimeStigma is a simple site to the point of making navigation and searching for content difficult. It has only a basic search that picks up titles, and A-Z lists of 2D and 3D hentai, besides a few top lists. There's no genre list even though each hentai episode is tagged accordingly. This means you'll either have to browse and use the genre tags to find related content or you'll have to know exactly what you're looking for. Besides that, you won't know if a hentai series from the list is subbed or not until you click on it. For favorites and comments, you can register, but you won't get more than that. Lastly, you will come across some pop-ups.
If you're patient enough to browse with limited sorting options, or if you know exactly what you're looking for, then Hentai Anime Stigma is a place you'll like and should visit. Here you can watch hundreds of series and thousands of free, full hentai episodes.