infallible (adj.)

• absolute
• acceptable
• agreeable
• certain
• chaste
• close
• constant
• correct
• delicate
• dependable
• direct
• effective
• efficacious
• efficient
• even
• exact
• express
• faithful
• faultless
• fine
• flawless
• foolproof
• handy
• helpful
• ideal
• immaculate
• impeccable
• inerrable
• inerrant
• irreproachable
• mathematical
• microscopic
• nice
• oracular
• peerless
• perfect
• precise
• pure
• refined
• reliable
• religious
• rigid
• rigorous
• satisfactory
• satisfying
• scientific
• secure
• severe
• sinless
• spotless
• square
• stainless
• strict
• subtle
• sure
• unadulterated
• unblemished
• uncontaminated
• undeviating
• unerring
• unfailing
• unmixed
• unspotted
• untainted
• useful