pungent, spicy, harsh, cruel, severe
辣 centers on a sharp, intense quality that can be physical (pungent, spicy) or figurative (harsh, cruel, severe). The idea is something that stings or bites, whether on the tongue or in behavior.
bitter (e.g. criticism); sharp; biting; severe; scathing; harsh
mala (spicy and numbing seasoning)
crafty; vicious; unscrupulous; sharp
Chinese onion (Allium chinense); Chinese scallion; Kiangsi scallion; rakkyo
shrewdness; sharpness; astuteness; acumen; tact
Japanese onion (Allium thunbergii)
laziji; spicy Sichuan chicken dish
hot-and-sour cabbage
hot and sour soup
hot and sour noodles (Szechuan dish)
malatang (Sichuan-style spicy street food)
辣 combines 辛 (spicy, bitter) with 束, which likely contributes a phonetic element. The character expresses the idea of sharp, pungent taste or harshness.
On the left, 辛 (spicy, bitter) already suggests a sharp taste. On the right, 束 (bundle) looks like a tied bunch of hot peppers. Together, they make 辣: a bundle of spicy, pungent heat.
For ラツ, imagine a rat (ラット) that ate something so spicy it starts running in circles: rat -> ラツ, and the spicy 辣 makes it go wild.