The first requirement for safe hashtable implementations is a secret key, which makes it impossible to know the hash value for an external observer. (Or even, to know the relative hash value between any two inputs.)
You can't force a collision for the function f(x) = x, by definition it has no collisions. It's not just collision-resistant, it's actually collision proof!
hash(x) = x is of course not a cryptographic hash, but it also has the advantage that it's unlikely to be confused for one if anyone looks at the output.
Every hashtable implementation will put the hash value through some sort of modulo because you generally don't want to waste memory storing the key 5726591 at index 5726591 in an array.
So if you know how the implementation works and the hash function is predictable you can keep providing the program with values that will consistently go into the same bucket resulting in linear lookups and insertions.
Some languages use different approaches. The buckets in a Java HashMap turn into a sorted tree if they grow too large. Then there are trivial solutions like adding an input limit for untrusted users. Either way works, is secure and doesn't depend on a secret key.