Lately I get asked this a lot by friends who want to subtitle or recommend horror flicks, so here's how I usually put it: the most natural Tagalog word for 'scary' is 'nakakatakot.' It’s what people say when a movie gives them the creeps — so you’d say, for example, 'Nakakatakot ang pelikula' or the casual 'Nakakatakot yung movie.'
If you want to vary the tone, there are several colorful alternatives: 'nakakakilabot' (gives you chills), 'nakapangingilabot' (more poetic or intense), and the mouthful 'nakakatindig-balahibo' (literally makes your hair stand on end). For something more dramatic in writing or reviews, 'kahindik-hindik' or 'nakahindik-hindik' conveys horror at a grander scale.
In casual chat I often hear people say 'Nakakatakot talaga' for emphasis, or 'Nakakakilabot naman!' if they mean spooky in a shivery, visceral way. Personally, I default to 'nakakatakot' because it sounds natural in conversation but I sprinkle in 'nakakakilabot' when I want to dramatize a scene — it just nails that goosebump feeling for me.