Derail…

Derail –

1. to cause to run off the rails

2. a. to obstruct the progress of

b. to upset the stability or composure of

Synonyms: agitate, ail, alarm (also alarum), bother,concern, disturb, discomfort, discompose, dismay, disquiet,distemper, distract, distress, exercise, flurry, frazzle, freak (out), fuss, hagride, perturb, undo, unhinge, unsettle, upset,weird out, worry

Antonyms: calm, compose, quiet, settle, soothe, tranquilize(also tranquillize)

Related Words: aggravate, anger, annoy, bug, chafe, chivy(or chivvy), exasperate, fret, gall, get, grate, harass, harry,irk, irritate, nettle, peeve, pester, pique, put off, put out,rile, vex; bedevil, haunt, plague; abash, confound, confuse,discomfit, disconcert, discountenance, embarrass, faze,fluster, jar, mortify, nonplus, rattle, shake up; daunt,demoralize, discourage, dishearten, dispirit, unnerve

***Above information courtesy Merriam-Webster on-line dictionary