Based on the Type Coverage Checker here on the sight, with only a Bug and Water move, you'll have 46 Pokemon that you can only hit "Not Very Effective...", along with Shedinja being immune to you. This is easily remedied by adding Night Slash for a Dark type move. This will give you at least neutral coverage against all but 7 Pokemon, most of them being Water, Fairy, or Fighting with a couple of Dragons. If Night Slash specifically is not your cup of tea, you can always use Knock Off instead via the Move Tutor.
Personally, I'd swap out Megahorn for X Scissor. Losing the 40 points of base damage might seem harsh, but frankly it's hard to beat higher accuracy. You'll get more PP for your trouble, as well. While you're at it, Liquidation is probably worth consideration over Razor Shell. 50% chance to reduce Defense might look like a huge deal, and it's thematically appropriate for sure, but you're gaining 10 base damage and 5 accuracy. If you were uncertain about Megahorn's low accuracy, you'd be slamming your face into the desk if miss on that 5%. Liquidation is also a Move Tutor move.