radioactive

abate, de-escalate, decline, decrease, die (away or down or out), diminish, drain (away), drop (off), dwindle, ease, fall, fall away, lessen, let up, lower, moderate, pall, phase down, ratchet (down) also rachet ​(down), recede, relent, remit, shrink, subside, taper, taper off, wanetrue'>, lag, languish, run down, sag, slip, waste (away), weaken, wilt

go to pot, go to seed (or run ​to ​seed)

better, upgrade

enhance, enrich, fortify, heighten, intensify, strengthen

advance, develop, march, proceed, progress

ameliorate, improve, meliorate

abate, de-escalate, decline, decrease, die (away or down or out), diminish, drain (away), drop (off), dwindle, ease, fall, fall away, lessen, let up, lower, moderate, pall, phase down, ratchet (down) also rachet ​(down), recede, relent, remit, shrink, subside, taper, taper off, wane