English words that seem to have opposite meanings, "sanction", "bash", "bashful"

Somebody in a forum mentioned a few English words that seem to have opposite meanings. One is "sanction", which according to Wiktionary means (1) an approval, by an authority, generally one that makes something valid; (2) a penalty, or some coercive measure, intended to ensure compliance; especially one adopted by several nations, or by an international body. A quick response from another guy is "really? somebody should tell Putin that sanction can mean something better!!" That's interesting! Anyway, I've always worried about the seemingly conflicting meanings of this word and sometimes avoid using it in my writing or speech, unless it's very clear, as in "economic sanction (against a country)".

Another example mentioned is "bash". On the one hand, it has the meaning of to strike heavily, to criticize harshly (source), as in "Bashing Hillary? Don't go there, GOP". On the other hand, the word "bashful" means shy, timid (source). How could you justify these two opposite human behaviors with one single word (or word with a suffix)? This word, though, is different from "sanction", in that "bashful" actually has a completely different etymology and is related to the verb "abash", to make ashamed or embarrassed (source). In any dictionary, when two words have the same spelling but are descended from two etymological sources, they're usually listed as two headwords or entries. In case of "bashful", it's not the word "bash" with the suffix "-ful", but was formed by "abashed" + "-ful" and later lost the initial unstressed vowel (a process called aphesis). "bash" does have the same meaning as "abash" except that sense is now obsolete.

Well, some words that look like having different meanings but they don't, such as "flammable" and "inflammable". That's another topic, for now.