Those that aren't "strict" in certain areas. Examples:

* Those without memory management (I'm not talking about garbage collection, though there seems to be a correlation). Buffer overflows/overruns and its cousins have caused many security flaws, including heartbeat and even flaws in java, where it interops with C programs for performance's sake.

* Syntactical leniency wrt. scope can lead to errors like apple's infamous "goto fail"

I didn't want to say, as most languages have their fans. But anything missing the features ML had; any language with null, without memory safety checking, without sum types and pattern matching, without type safety or generics (really any language without HKT, though I guess you don't need it for small programs).