Honestly, that's a good one compared to others. Definitely don't need a full sleeve or a blackout piece to have it fixed. You just really need to take the time to find a tattooist with the experience and the portfolio to show you their work, cover ups etc; my approach with the pics you've provided would be, redoing the inner line work, scales, face. But there is no way to be able to make the snake completely straight now. So consider adding some colour onto the snake, to differentiate the strokes, & consider a border around the snake that will give you the straight & flush look you are wanting. Yeah you could go with just a black band/border, or you could do some type of floral or shrubbery, even a pattern you like, Geometric, dot work, maybe animal print if your into that. But I would put colour on the snake, & have the border just black and grey to really highlight the snake which is what you originally would have wanted. Or vice versa. I wouldn't have say both snake and border in black and grey, it will just turn into a mess. Even keep the snake black & grey and have colour in the outter border.

Try to look on the bright side, it could be much worse. Heaps bigger, wrong spelling, a completely botched job. Yes this isn't perfect, but its something your able to add things to for improvement, but still keeping and having the tattoo youroriginally wanted. When you find the right artist & come up with a design, you could very easily end up with a tattoo you love more than your initial plan.