〜にくい— Hard to do (Structural Difficulty)

• この字は読みにくいです。

  Kono ji wa yominikui desu.

  This handwriting is hard to read.

  読み (read, masu-stem) + にくい (structurally difficult)

• この肉は固くて食べにくい。

  Kono niku wa katakute tabenikui.

  This meat is tough and hard to eat.

  食べ + にくい = physically tough to chew

• 雨の日は運転しにくい。

  Ame no hi wa unten shinikui.

  It is hard to drive on rainy days.

  運転し + にくい = environmental difficulty

• ・にくい vs づらい: Both mean "hard to do". にくい refers to inherent/physical difficulty (meat is physically tough to chew = 食べにくい). づらい refers to emotional/mental burden (I feel bad eating it = 食べづらい).
• ・Adjective Conversion: When にくい attaches to a verb, the whole word becomes an い-adjective and conjugates like one (読みにくかった).

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones 〜にくい is tested against.

• たことがある — Have Done (Experience)
• つもりだ — Intention / Plan
• ほうがいい — Had Better / Should
• てほしい — Want someone (else) to do something
• だけで — Just by doing / With just
• ではないか / じゃないか — Isn't it? (rhetorical)
• が必要だ (がひつようだ) — Need / Necessary
• がする — Involuntary sense perception