Spine should work according to SimonS. I don't have any documentation for it, so I've no idea how to actually use it myself or where to even begin. I also don't own Spine.
What do you mean by 250 images? Are you talking about 250 frames in a single animation or are you talking about 250 frames spread out over various animations for said giant? Because I can't recommend 250 frames for any single animation. At most you should be aiming for about 24 frames or less per any animation, though you can use more if you want.
Quick tip #1: VS accepts webp image format. I highly recommend you convert all your png / jpg files to webp lossy quality 100 as it's hard to distinguish the difference between those & lossless png versions, plus you get the bonus of massively reduced file-sizes when using webp (anything up to 50% less than the original png file-size), which means your animations / images will load much faster than png versions.https://wiki.visionaire-tracker.net/wiki/Image_Encoding
Quick tip #2: Try to refrain from using duplicated animation frames for the sake of making your animations look smoother. I am talking about using the same image multiple times in a row (different files) as you can specify the delay / pause value manually between each animation frame if you so choose. You can also manually insert new animation frames & you can also control the global delay / pause value between all frames, as well as the playback order (forwards, backwards or random - we don't have a pendulum option yet, but I think I will put in a request for it to be added at some point).https://wiki.visionaire-tracker.net/wiki/Game_Optimization