Up: Smalltalk
Reasons:
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It is tough or impossible to use existing tools or libraries. This means that many things are reinvented (version control systems, network libraries).
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It isn’t realistically possible to use external editors.
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There is no single syntax; each Smalltalk implementation has its own syntax. There is also no commonly agreed-upon standard library, which makes writing cross-implementation libraries tough.
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In my experience, Smalltalk images can get damaged/corrupted rather quickly.